noaa nautical chart user's manual 1997

NAUTICALCHART USER’S

MANUAL

U.S. DEPARTMENT OF COMMERCENational Oceanic and Atmospheric Administration (NOAA)National Ocean Service

Washington, DC, 1997

Table of Contents i

TABLE OF

CONTENTS

Preface and Acknowledgments ...................................................................................... ix

Chapter 1 Introduction

Background ............................................................................................................ 1-1The Nautical Chart User's Manual ..................................................................... 1-3Organization of this Manual ................................................................................. 1-4Relevant Facts, Statistics, and Products ............................................................. 1-5Purpose of the Nautical Chart .............................................................................. 1-7How Does a Nautical Chart Differ from a Map? ................................................. 1-8

�An Illustrative Chart .................................................................................... 1-8�An Illustrative Map .................................................................................... 1-10

User Groups ......................................................................................................... 1-10Efficiency of Chart Compared to Text ................................................................ 1-12Chart Distribution�Where to Purchase Charts .............................................. 1-13

�Mail Order Sales ......................................................................................... 1-13�Authorized Chart Agents ............................................................................ 1-13�The Nautical Chart Catalog ...................................................................... 1-13

Chart Prices and Related Matters ...................................................................... 1-13Chart Demand ..................................................................................................... 1-15ECDIS, The End of the Paper Era? .................................................................... 1-16Chart-Related Publications ................................................................................. 1-17

�Chart No. 1 .................................................................................................. 1-17�Chart Catalogs ............................................................................................ 1-17�Dates of Latest Editions ............................................................................. 1-17�Notice to Mariners ...................................................................................... 1-17�Local Notice to Mariners ............................................................................ 1-19�U. S. Coast Pilot ......................................................................................... 1-20�Light List .................................................................................................... 1-20�Tide Tables and Tidal Current Tables ...................................................... 1-21

The Track Ahead ................................................................................................. 1-21

Chapter 2 General Information and Overview

Introduction ............................................................................................................ 2-1Chart No. 1 ............................................................................................................ 2-1Schematic Layout of a Nautical Chart ................................................................ 2-2Number, Title, and Marginal Notes (A) .............................................................. 2-2Latticed Charts (A) ................................................................................................ 2-6Edition (A) .............................................................................................................. 2-6Reconstructed, Provisional, and Preliminary Charts......................................... 2-6

�Importance of Current and Corrected Charts ............................................ 2-8Source Diagram (A) ............................................................................................... 2-9Neatline Dimensions (A) ....................................................................................... 2-9

NOAA Chart User's Manualii

Chapter 2 General Information and Overview (cont'd.)

Chart Title, Authorities Note, and Seal (A) ......................................................... 2-9Projection and Scale (A) ........................................................................................ 2-9

�Projections ..................................................................................................... 2-9�Chart Scale .................................................................................................. 2-11�Chart Types ................................................................................................. 2-13�A Mix of Charts Necessary ........................................................................ 2-14

A Brief Aside, Chart Storage and Care�Rollers versus Folders ..................... 2-16Linear and Logarithmic Speed Scales (A) ......................................................... 2-17Notes and Cautions ............................................................................................. 2-18Chart Overlap, Insets, and Related Matters ..................................................... 2-19

Measures to Minimize Confusion: The Chartmaker's Perspective ........... 2-19Measures to Minimize Confusion: The Navigator's Role ........................... 2-21

Latitude, Longitude, Regular, and Skewed Projections ................................... 2-25Depth Units and Vertical Datum ....................................................................... 2-25Horizontal Datum................................................................................................ 2-26

Relevance of Horizontal Datum ................................................................... 2-26Direction and Magnetics (B) ............................................................................... 2-27

Compass Roses (B70) .................................................................................... 2-27Local Magnetic Disturbance Notes ............................................................. 2-27Isogonic Lines (B 71) ..................................................................................... 2-29

Additional Information ........................................................................................ 2-29Lettering Styles (Vertical versus Slant Type) ................................................... 2-31Use of Color on Charts ........................................................................................ 2-31Symbols and Abbreviations ................................................................................. 2-31Use of Charts ....................................................................................................... 2-31

Chapter 3 Topography and Related Information

Introduction and Overview ................................................................................... 3-1Utility of this Information and Implications for Chart Design.......................... 3-2Coastline/Shoreline (C 1 - C 8) .............................................................................. 3-3

�Shoreline Plane of Reference ........................................................................ 3-4�Apparent Shoreline (C 32, C 33) .................................................................. 3-4�Approximate or Unsurveyed Shoreline (C 2) .............................................. 3-4�Flat Coast (C 5) ............................................................................................. 3-4�Steep Coast�Bluff; Cliff (C 3) ........................................................................ 3-4�Surveyed Coastline (C 1) .............................................................................. 3-5�Other Shoreline Types .................................................................................. 3-5�Foreshore ....................................................................................................... 3-5�Chart Sounding Datum Line (C a) .............................................................. 3-5�Approximate Sounding Datum Line (C b) .................................................. 3-5�Breakers ........................................................................................................ 3-5�Grass .............................................................................................................. 3-5�Mud/Sand/Stone or Gravel/Sand and

Mud/Sand and Gravel/Rock/Coral/Rubble.............................................. 3-5�Illustration..................................................................................................... 3-6

Elevation and Relief Data...................................................................................... 3-6�Land Contours C 10)..................................................................................... 3-6�Approximate Contour Lines (C 12) .............................................................. 3-9�Peaks (C 10, C 11) and Treetop Elevations (C 14)...................................... 3-9�Hachures ....................................................................................................... 3-9�Height of Object .......................................................................................... 3-10�An Aside: Indirect Use of Terrain Information ........................................ 3-10

Table of Contents iii

Chapter 3 Topography and Related Information (cont'd.)

Inland Waters ...................................................................................................... 3-12�Glaciers (C 25) ............................................................................................. 3-12�Intermittent Rivers and Streams (C 21) ................................................... 3-12�Lakes and Ponds (C 23); Lagoons (C h) .................................................... 3-12�Rapids and Waterfalls (C 22) ..................................................................... 3-12�Rivers and Streams (C 20) ......................................................................... 3-12�Salt Pan (C 24) ............................................................................................ 3-12

Trees ................................................................................................................. 3-12Lava Flow (C 26) .................................................................................................. 3-12Vegetation (C o, C j, C l, C i, C m, C n, C k, C 30) ........................................... 3-12Marshes and Swamps (C 32, C 33)..................................................................... 3-13Ports and Harbors ............................................................................................... 3-13

�Berthing Structures .................................................................................... 3-13�Additional Sources ...................................................................................... 3-16

Erosion�Control Structures ................................................................................ 3-17�Breakwater (F 4.1) ...................................................................................... 3-17�Groins (F 6.1, F 6.2, F 6.3) ........................................................................ 3-17�Jetties (F a, F b, F c) .................................................................................. 3-17�Seawall (F 2.1, F 2.2) .................................................................................. 3-17�Dikes and Levees (F 1) ............................................................................... 3-17�Additional Sources ...................................................................................... 3-18

Docks and Tidal Basins....................................................................................... 3-18�Dry Dock, Graving Dock (F 25) ................................................................. 3-18�Tidal Basin (F 28) ....................................................................................... 3-18�Wet Dock (F 27) .......................................................................................... 3-18�Additional Sources ...................................................................................... 3-18

Bridges (D 22 � D 24, D d, D e) .......................................................................... 3-18�Bridge Symbols (D 22 - D 24, D d, D e) and Related ................................ 3-19�Hazards Under Bridges .............................................................................. 3-20�Bridge Clearances (D 20, D 21) .................................................................. 3-21�Names .......................................................................................................... 3-22�VHF Radio Capability ................................................................................. 3-22�Additional Sources ...................................................................................... 3-22�Illustration................................................................................................... 3-22

Locks and Other Barriers ................................................................................... 3-23�Locks (F 41.1, F 41.2) ................................................................................. 3-23�Floodgates, Sills, and Miscellaneous Other .............................................. 3-24

Landing and Launching Sites ............................................................................ 3-24�Marine Railway (F 23) ................................................................................ 3-24�Ramps (F 23) ............................................................................................... 3-24

Artificial Features ............................................................................................... 3-24�Roads and Related ....................................................................................... 3-24�Cable Ferry (M 51) ...................................................................................... 3-24�Canal (F 40) ................................................................................................. 3-25�Dam (F 44)................................................................................................... 3-25�Ditch (F 40) ................................................................................................. 3-25�Pipelines on Land (D 29) ............................................................................ 3-25�Railroads (D b) ............................................................................................. 3-25�Roads and Road Patterns (D 1, D 2, D 10, D 11, D a) ............................. 3-25�Trails (D 12) ................................................................................................ 3-25�Tunnel Entrances (D 16) ............................................................................ 3-26

NOAA Chart User's Manualiv

Chapter 3 Topography and Related Information (cont'd.)

Buildings and Structures .................................................................................... 3-26�Airports (D 17, N e) .................................................................................... 3-26�Buildings (D 5, D 6, E d, F 61, F 62.2, F 63) and Tanks (E 32) ............. 3-26�Illustration................................................................................................... 3-27�Cemeteries (E 19) ........................................................................................ 3-27�Church Buildings (E 10.1 - E 18)............................................................... 3-27�Hospitals (F 62.2) ........................................................................................ 3-27�Urban Screen .............................................................................................. 3-27

Miscellaneous Stations ........................................................................................ 3-27�USCG Stations (T 10, T 11) ....................................................................... 3-28�Fireboat Station (T d) ................................................................................. 3-29�Marine Police Stations (T c) ....................................................................... 3-29�Pilot Stations (T 3) ...................................................................................... 3-30

Overhead Cables and Crossings (D 26, D 27) .................................................... 3-30�Overhead Cable Cars (D 26) ....................................................................... 3-30

Land Boundaries and Limits .............................................................................. 3-30Key Points and Miscellaneous Comments ......................................................... 3-30Concluding Comments ........................................................................................ 3-32

Chapter 4 Hydrography and Related Information

Introduction and Overview ................................................................................... 4-1�A Brief Aside: Dual Units ............................................................................ 4-1

Utility of Hydrographic and Related Information ............................................... 4-2Hydrographic Information .................................................................................... 4-3

�Common Plane of Reference and Survey Scales ......................................... 4-3�Source Diagrams ........................................................................................... 4-5

Soundings ............................................................................................................... 4-5�The Soundings Selection Challenge ............................................................. 4-6�Selection Criteria for Soundings to be Charted .......................................... 4-7�Charting Practices ...................................................................................... 4-10

Depth curves (Section I of Chart No. 1) ............................................................. 4-10�Charting Practices ...................................................................................... 4-12�Symbol ......................................................................................................... 4-13�Labels ........................................................................................................... 4-13�Shallow Water Tint(s) ................................................................................ 4-13�Improved (Artificial) Channels ................................................................... 4-13�Symbols........................................................................................................ 4-15

Bottom Characteristics ....................................................................................... 4-15Specific Hazards to Navigation .......................................................................... 4-15Danger Curve (K 1) ............................................................................................. 4-18

�Charting Practices ...................................................................................... 4-18�Labels and Notes ......................................................................................... 4-18

Rocks (K 10-17, a, b, f) ........................................................................................ 4-18�Charting Practices ...................................................................................... 4-23�Rocks Symbols and Labels ......................................................................... 4-23�Bare Rock ( 10) ............................................................................................ 4-23�Rocks Which Cover and Uncover (K 11) ................................................... 4-23�Rocks Awash at the Level of Chart Datum (K 12) ................................... 4-23�Sunken Rocks (K 2, 13) .............................................................................. 4-23�Doubtful Danger Labels ............................................................................. 4-24

Shoals (K b, O 25) ................................................................................................ 4-24�Charting Practices ...................................................................................... 4-26

Table of Contents v

Chapter 4 Hydrography and Related Information (cont'd.)

Ledges and Reefs (Various) ................................................................................. 4-26�Charting Practices ...................................................................................... 4-26

Foul Area (K 31)................................................................................................... 4-26�Charting Practices ...................................................................................... 4-27�Symbol (K 31) .............................................................................................. 4-27�Label(s) and Notes ...................................................................................... 4-27

Wrecks and Hulks (K 20-31) .............................................................................. 4-27�Charting Practices ...................................................................................... 4-27�Symbols, Labels, and Tints ........................................................................ 4-27�Wrecks Marked by Buoys .......................................................................... 4-28

Obstructions (K 40-42) ........................................................................................ 4-28�Charting Practices ...................................................................................... 4-29�Symbols and Labels .................................................................................... 4-29

Natural Dangers (K 43.2) ................................................................................... 4-29Fish Havens Regulated by State and Federal Permits (K 46.1, K 46.2)......... 4-29

�Charting Practices ...................................................................................... 4-29Miscellaneous Hazards ........................................................................................ 4-30Unexploded Ordnance ......................................................................................... 4-30

�Charting Practices ...................................................................................... 4-30�Symbols........................................................................................................ 4-30�Labels and Notes ......................................................................................... 4-30

Unsurveyed Area (I 25) ....................................................................................... 4-30�Charting Practices ...................................................................................... 4-31

Dangerous Water Conditions (Various) ............................................................. 4-31�Charting Practices ...................................................................................... 4-31�Symbols........................................................................................................ 4-31�Labels and Notes ......................................................................................... 4-31

Submarine Pipeline and Cables (L 30.1�44 ..................................................... 4-32�Submarine Pipelines (L 40.1, 40.2, 41.1, 41.2, 43, 44) ............................ 4-32�Individual Pipelines .................................................................................... 4-32�Pipeline Areas ............................................................................................. 4-33�Submarine Cables (L 30.1, 30.2, L 31.1, L 32) ........................................ 4-33�Individual Cables ........................................................................................ 4-33�Cable Areas .................................................................................................. 4-34

Other Relevant Sources of Information ............................................................. 4-34U.S. Coast Pilot................................................................................................... 4-34Tide Tables and Tidal Current Tables ............................................................... 4-35Notice to Mariners ............................................................................................... 4-35Local Notice to Mariners ..................................................................................... 4-35Concluding Remarks ........................................................................................... 4-35

Chapter 5 Aids to Navigation

Introduction and Overview ................................................................................... 5-1Brief Historical Asides ........................................................................................... 5-2Importance of ATONs in Coastal Navigation...................................................... 5-2Importance of Positive Identification and Related Matters ................................ 5-2ATONs and Related Chart Information (General) .............................................. 5-4

NOAA Chart User's Manualvi

Chapter 5 Aids to Navigation (cont'd.)

Lights ................................................................................................................... 5-6�Charting Practices ........................................................................................ 5-7�Symbol (P) ..................................................................................................... 5-7�Labels and Notes ........................................................................................... 5-7�Sectors and Related Matters ...................................................................... 5-11�Directional Lights ....................................................................................... 5-11�Leading Light .............................................................................................. 5-14�Aeronautical Lights .................................................................................... 5-14�Articulated Lights....................................................................................... 5-14�Strobe Lights ............................................................................................... 5-14�Riprap .......................................................................................................... 5-15

Supplemental Information Regarding Lights and Other ATONs ................... 5-15�The U.S. Coast Guard Light List .............................................................. 5-15�The U.S. Coast Pilot .................................................................................. 5-16�Published Guides and Other Books ........................................................... 5-16

Buoys ................................................................................................................. 5-17�A Brief Digression: Position Fixing with Buoys ....................................... 5-18�Charting Practices ...................................................................................... 5-20�Symbols (Q) ................................................................................................. 5-20�Charted Characteristics ............................................................................. 5-23�Channel Buoys ............................................................................................ 5-25�Junction Buoys ............................................................................................ 5-26�Midchannel Buoys....................................................................................... 5-26

Fog Signals (R) ..................................................................................................... 5-26�Charting Practices ...................................................................................... 5-27�Labels and Notes ......................................................................................... 5-27

Daybeacons (Q) .................................................................................................... 5-28�Charting Practices ...................................................................................... 5-29�Daybeacon Symbols .................................................................................... 5-29�Daybeacon Labels ....................................................................................... 5-29

Ranges (M)............................................................................................................ 5-31�Charting Practices ...................................................................................... 5-32�Symbol (M 1) ............................................................................................... 5-32�Range Labels ............................................................................................... 5-32�Dredging Ranges ......................................................................................... 5-32�Natural Ranges ........................................................................................... 5-32

Radiobeacons and Related Aids (S) ..................................................................... 5-32�Charting Practices ...................................................................................... 5-34�Symbol (S 1) ................................................................................................. 5-34�Labels ........................................................................................................... 5-34�Aeronautical Radiobeacons ......................................................................... 5-35

Miscellaneous Related Information .................................................................... 5-35�Measured Course (Q 122) ........................................................................... 5-35

Concluding Remarks ........................................................................................... 5-36

Chapter 6 Landmarks

Introduction and Overview ................................................................................... 6-1Importance of Landmarks in Coastal Navigation .............................................. 6-1Types of Landmark ............................................................................................... 6-3Objects Not Normally Depicted as Landmarks .................................................. 6-6

Table of Contents vii

Chapter 6 Landmarks (cont'd.)

How Landmarks Are Depicted on the Chart ....................................................... 6-7�Symbols.......................................................................................................... 6-7�Labels ............................................................................................................. 6-9�Other Sources of Landmark Information ................................................. 6-11

Practical Pointers and Limitations Relevant to Landmarks........................... 6-12�Pointers........................................................................................................ 6-12�Selecting Landmarks For Use ................................................................... 6-12�Limitations .................................................................................................. 6-15

Concluding Comments ........................................................................................ 6-19

Chapter 7 Areas, Limits, Tracks, and Routes

Introduction and Overview ................................................................................... 7-1Utility of This Information ................................................................................... 7-1Federally Regulated Areas (N 1.2, N 2.2, N 31) ................................................. 7-2

�Regulated Navigation Areas ........................................................................ 7-2�Danger Area .................................................................................................. 7-2�Seaplane Restricted Areas/Seaplane Operating Areas (N 13, N 14) ......... 7-2�Restricted Area (N 20) .................................................................................. 7-3�Safety Zones/Defense Areas/Security Zones ................................................ 7-3�Relevance to the Mariner ............................................................................. 7-5�Charting Practices ........................................................................................ 7-5�Symbol (e.g., N 1.2, N 2.2, N 31) ................................................................ 7-5�Labels and Notes ........................................................................................... 7-5�Examples ....................................................................................................... 7-7�Illustrative Regulations ................................................................................ 7-8�Summary ..................................................................................................... 7-10

Civil Reservations ................................................................................................ 7-10�Charting Practices ...................................................................................... 7-10�Symbol (N 22) .............................................................................................. 7-10�Labels and Notes ......................................................................................... 7-10�Relevance to the Mariner ........................................................................... 7-10

Federally Regulated Anchorage Areas/Grounds................................................ 7-11�Anchorage Grounds .................................................................................... 7-11�Special Anchorage Areas ............................................................................ 7-12�Fairway Anchorages ................................................................................... 7-12�Relevance to the Mariner ........................................................................... 7-12�Charting Practices ...................................................................................... 7-14�Symbol (e.g., N 11.1 - N 20) ....................................................................... 7-14�Label ............................................................................................................ 7-14�Notes ............................................................................................................ 7-14

Nonfederally Regulated Anchorages (N 12.1) .................................................... 7-15Harbors of Refuge (N 10) ..................................................................................... 7-16Dumping/Disposal Areas ..................................................................................... 7-16

�EPA�Established Dumping Areas (N 24, N c, N d, N g) ........................ 7-17�Navy�Established Dumping Areas ........................................................... 7-17�U.S. Army Corps of Engineers Areas ........................................................ 7-17�Dumping Grounds (N c) ............................................................................. 7-18�Relevance to the Mariner ........................................................................... 7-18�Illustration................................................................................................... 7-18

NOAA Chart User's Manualviii

Chapter 7 Areas, Limits, Tracks, and Routes (cont'd.)

COLREGS Demarcation Line (N a) ................................................................... 7-20�Charting Practices ...................................................................................... 7-20�Symbol (N a) ................................................................................................ 7-20�Label ............................................................................................................ 7-20

Degaussing Range (N 25) .................................................................................... 7-21Maritime Boundaries ........................................................................................... 7-21

�International Boundaries (N 40, N 41) ..................................................... 7-21�Exclusive Economic Zone (N 47) ................................................................ 7-21�Closing Line/Three Nautical Mile Line/

Territorial Sea and Contiguous Zone (N 42, N 43, N 44) ................... 7-22Traffic Separation Schemes and Related Matters ............................................. 7-24

�Notes ............................................................................................................ 7-29�Additional Information ............................................................................... 7-29�Relevance to the Mariner ........................................................................... 7-30�Smaller Vessels ........................................................................................... 7-30

Course Lines ........................................................................................................ 7-31Courses7-32Concluding Comments ........................................................................................ 7-32

Appendix A Glossary .................................................................................................... A-1

Appendix B Abbreviations

Part I Index of Abbreviations (Section V of Chart No. 1) .......................... B-1Part II Index of Abbreviations�Supplementary National

Abbreviations (Section V of Chart No. 1) ......................................... B-6Part III International Abbreviations (Section W of Chart No. 1) ................ B-9Part IV Abbreviations used this Manual, NM, LNM,

Light List, Broadcast Notice To Mariners,Nautical Chart Catalog, or Dates of Latest Editions ...................B-11

Preface and Acknowledgments ix

PREFACE AND

ACKNOWLEDGMENTS

Many products are sold with user�s manu-als. Some, such as those for an aircraft, auto-mobiles, or pieces of electronic equipment,are quite voluminous and complex. Others aremore modest. A �patented insect destruction�novelty device sold several years ago con-sisted of only two small wooden blocks. Eventhis novelty device came with a user�s manual;it consisted of a single sheet of paper with thefollowing instruction, �place insect on face ofone block and firmly place second block ontop of first block.�

Generally speaking, the more sophisti-cated and important the item, the more elabo-rate the user�s manual. The modern nauticalchart is reasonably complex and certainly anessential tool for the mariner. Yet, aside frompassing mention in textbooks on navigationand the publication of Chart No. 1, no user�smanual had been published for the nauticalchart. Arguably, such a publication is longoverdue.

This manual explains what is presentedon the nautical chart, highlights the utilityof this information, describes the chartingconventions used to depict features and itemsof interest, and provides some practicalpointers on how this information is used. Itis written to serve many types of users, rang-ing from operators of recreational vessels tothose who drive �heavy iron.�

Abundant photographs and chart excerptsillustrate key points made in the text. Allchart excerpts were current as of spring 1995.

Since this manual was published, some chartsmay have been revised. Even if these specificcharts have been revised, the general pointsremain valid. It almost goes without sayingthat these chart excerpts should not be usedfor navigational purposes.

This manual also identifies other publica-tions, such as the U.S. Coast Pilot, Tide Tables,Tidal Current Tables, Notices to Mariners, andthe U.S. Coast Guard's Light List which giveaddit ional re levant information to chartusers. Excerpts from these publications arealso provided in the manual. As with chartexcerpts, these may also have been revised.

The writing style is less formal than thatemployed in many government publications�designed to make the manual more �user-friendly� in today�s vernacular. The manualis authoritative, but not encyclopedic. Tokeep the manual to a manageable size, onlythe most important topics are included.

This is a chart user�s manual, and not atextbook on seamanship or navigation. None-theless, nautical charts are used principallyfor navigational purposes and, therefore,some basic elements of the theory and prac-tice of navigation are included in this manual.References that provide additional and moredetailed discussions of relevant aspects ofnavigation are included at the end of eachchapter. Inclusion of these references in thismanual does not mean that the NationalOceanic and Atmospheric Administration (NOAA)or any other agency of the U.S. government

NOAA Chart User's Manualx

out the project. A Committee consisting ofCAPT David MacFarland, NOAA, MarkFriese, Robert Rodkey, Erich Frey, NelsonGarber, Jason Rolff, John Ondrejko, RonaldStuckey, Thomas Dade, Stanley Weiss, KenO'Dell, Eric Johnston, and LCDR MarleneMozgala, NOAA, provided direction and ex-pertise in developing and reviewing the ChartUser's Manual. In addition, Ira Dolich and An-drew Ritzie (both USCGAUX) made helpfulcomments and suggestions which improvedthe quality of this manual. Credit, therefore,should be shared among many. The responsi-bility for errors and omissions rests solelywith the author.

Special thanks to Dottie Brown for her at-tention to detail on the final edit of this manu-script.

Cranbury, NJDecember 1997

agrees with any findings, conclusions, or opin-ions contained in these references. Likewise,inclusion of any trade names or photographsof specific equipment does not constitute aproduct endorsement.

The creation of this manual was a coopera-tive project between NOAA and the UnitedStates Coast Guard Auxiliary (USCGAUX), thevolunteer civilian component of the U.S. CoastGuard. Dr. L. Daniel Maxim (DVC�ER,USCGAUX) wrote the manual. Mrs. VirginiaL. Knudsen (DC�EX, USCGAUX) ablyhandled the layout and graphics. Many NOAApersonnel made important contributions,notably CAPT Thomas Richards, NOAA,Messrs. Harold Schantz and Jeff Stuart whoshared a common vision of excellence, alwaysresponded patiently to questions and providedconstructive criticism and guidance through-

Introduction 1-1

CHAPTER 1

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Fig. 1-1. Principal NOAA Chart/Map Products

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Introduction 1-7

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Introduction 1-9

Fig. 1-2. Excerpt from NOS Chart 12314 (Delaware River, Philadelphia to Trenton)Showing Portion of Delaware River in the Vicinity of Riverside, NJ, at a Scale of 1:20,000


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Introduction 1-11

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Fig. 1-4. A Typology of Nautical Chart Users

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Introduction 1-13

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The Nautical Chart Catalog Provides Ordering Information for NOAA Charts.

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Introduction 1-15

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Figure 1-5. Recent Sales History of NOAA/NOSNautical Charts: A Reflection of Evolving Tech-

nology or an Ominous Trend?

SOURCE: NATIONAL RESEARCH COUNCIL

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Introduction 1-17

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Dates of Latest Editions is an indispensable aid tothe mariner.

Chart No. 1 Provides Essential Information onsymbols and Conventions Used on

NOAA and NIMA Charts

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AUTOMATED NOTICE TO MARINERCHART CORRECTION QUERY SYSTEM

EXTRACT ALL CORRECTIONS TO SELECTED CHARTSTHRU CURRENT NTM 12/95

S 12314 28Ed.10/17/92 NEW EDITION (NOS; CL1126/92) 4/93A d d Purple dashed lines joining

40deg 06min 15.5sec N 74deg 49min 56.5sec W40deg 06min 13.0sec N 74deg 50min 14.0sec W40deg 05min 56.0sec N 74deg 50min 26.0sec W40deg 05min 50.2sec N 74deg 50min 24.0sec W

between40deg 05min 51.0sec N 74deg 50min 14.0sec W40deg 06min 05.3sec N 74deg 50min 03.0sec W

Legend "Cable Area''40deg 06min 07.0sec N 74deg 50min 12.0sec W

(Previously published 46/92)

A d d Tabulation of controlling depthsfrom back of Section I

12314 28Ed.10/17/92 LAST NM 04/93 (NOS) 14/93Change Characteristic of range light,

front to Oc R 4s40deg 07min 18sec N 74deg 46min 42sec W

rear to Oc R 4s40deg 07min 18sec N 74deg 46min 41sec W

S 12314 28Ed.10/17/92 LAST NM 14/93 (30/93 CG5) 36/93A d d Buoys, each Y, Fl Y 6s (Priv maintd)

"N'' 40deg 02min 01.2sec N 74deg 59min 40.0sec W"S'' 40deg 02min 00.0sec N 74deg 59min 41.6sec W

S 12314 28Ed.10/17/92 LAST NM 36/93 (CL978/93) 40/93A d d Tabulation of controlling depths

from back of Section I

S 12314 28Ed.10/17/92 LAST NM 40/93 (CL1268/93) 8/94A d d Tabulation of controlling depths

from Subsection I-2

S 12314 28Ed.10/17/92 LAST NM 08/94 (22/94 CG5) 28/94Change Legend to

"Q 21ft (Day), QR 21ft (Night)''

3/11/95

Figure 1-6. ANMS Output for NOS Chart No. 12314

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Introduction 1-19

Figure 1-7. Form for Recording NM Corrections

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CHART. PUB. NO. I PORTFOLIO NO. I EDITION NO./DATEICLASS PRI~E CORR [CTED THAU N. TO M., NO.lYR. OR PUB. CHANGES

TITLE

-APPLICABLE NOTICE TO MARINERS

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The United States Coast Pilot ProvidesA Wealth of Additional Information

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Introduction 1-21

Tide Tables and Tidal Current Tables, Issued Annually,Provide Daily Tide and Tidal Current Information

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Introduction 1-23

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General Information and Overview 2-1

IntroductionThis chapter provides additional general

information about nautical charts togetherwith specific information about the schematiclayout of a nautical chart, the chart titleblock, chart projections, types (and scale) ofcharts, chart overlap (and related matters),latitude and longitude axes, vertical and hori-zontal datums, isogonic lines and the compassrose, chart colors, chart lettering, and othermiscellaneous charting conventions. Whereappropriate, comments on the utility of thisinformation are included, as are practical tipson how to use this information.

Many specialized terms used in this chap-ter are defined in the Glossary in appendixA. Abbreviations are included in appendix B.Names enclosed in parentheses (e.g.,Bowditch) refer to sources listed at the endof this chapter that contain additional relevantdetail or useful general discussions.

It is recommended that the reader have anautical chart and Chart No. 1 at hand whenstudying the contents of this and subsequentchapters.

Chart No. 1As noted in Chapter 1, Chart No. 1, Nauti-

cal Chart Symbols, Abbreviations, and Terms(9th ed.), provides an indispensable descriptionof the symbols (both national and international)and many of the conventions used on the nau-tical chart. Chart No. 1 should be carriedaboard all vessels. The contents of Chart No. 1provide a useful framework for organizing thismanual. Although space constraints do not per-mit inclusion of Chart No. 1 in its entirety inthis manual, many illustrative excerpts are pro-vided.

Chart No. 1 is organized into various sec-tions, each providing information on one or moregroups or classes of symbols and conventionsused on the nautical chart. For example, gen-eral information is included in Section A (ChartNumber, Title, Marginal Notes); information onpositions, distances, directions, and the compassis presented in Section B; topographic featuresin Sections C through G; hydrographic informa-tion in Sections H through O; aids and servicesin Sections P through U; and alphabetical indi-ces in Sections V through X. Within each Sec-

CHAPTER 2

General Informationand Overview

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

�It is established for a custom of the sea that ifa ship is lost by default of the lodesman, the mari-ners may, if they please, bring the lodesman to thewindlass and cut off his head without the marinersbeing bound to answer before any judge, becausethe lodesman had committed high treason againstthe undertaking of the pilotage, and this is the judge-ment.�

Twenty-Third Article of the Laws of Oleron 1190

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Quoted in Schofield


tion of Chart No. 1 there are several subsec-tions, and numerous individual symbols arepresented within each subsection. For example,Section F contains port information, which isfurther subdivided into hydraulic structures,harbor installations, canals, transshipment fa-cilities, and public buildings. Within the sub-section on harbor installations F14 is the spe-cific symbol used to depict a pier or jetty.Where appropriate, these sections and symbolsare provided (e.g., F14) in the text or headingsof this manual to refer the reader to the relevantsection or symbol listed in Chart No. 1.

Charts published in the United States in-clude those produced by NOAA, NOS�forU.S. waters�and NIMA, for other areas of theworld. Symbols used by each agency aredepicted in Chart No. 1.

Because of the importance of Chart No. 1,it is worthwhile to summarize briefly the sche-matic layout of this chart. Figure 2�1 illustratesthis layout. Item 1 in this figure is the section(�Rocks, Wrecks, Obstructions�), and item 2 thesection designation (�K� in this illustration).Item 3 denotes the subsection (�Wrecks�), anditem 4 (�Supplementary National Symbols�)provides a reference to any supplementary na-tional symbols given at the end of each section.As the name implies, supplementary nationalsymbols are unique to each country (e.g., thoselisted in Carte No. 1, Chart 5011) and do notconform to the standard symbols authorized bythe IHO. Although not officially listed by theIHO, these supplementary national symbolshave been retained for the convenience of chartusers in each country. Standardized symbolsfacilitate chart use by mariners from differentcountries, while supplementary national sym-bols provide the flexibility to describe country-specific features and reflect historical chartingpractices.

Item 5 in figure 2�1 provides a cross-refer-ence to terms contained in other relevant sec-tions of Chart No. 1. In this illustration, thePlane of Reference for Depths, found in SectionH, is relevant to information given in Section K.Item 6 (column 1) identifies the standard num-ber which follows the �Standard List of Sym-bols, Abbreviations, and Terms� defined byI H O .

Item 7a in figure 2�1 is the symbol or rep-resentation as used on charts produced byNOAA. In many cases, the identical symbol isalso used by NIMA. If not, as in this example,the NIMA symbol is provided in an additionalcolumn (item 7b). Item 8 (�Stumps of posts orpiles, fully submerged�) is a written descrip-tion of the various terms or abbreviationsassociated with this symbol. Item 9 presentsthe chart symbol as prescribed/recommendedby the IHO. Finally, item 10 presents the cor-responding symbols that may appear on NIMAreproductions of foreign charts.

The reader interested principally in usingNOAA charts should focus on items 1, 2, 3, 4, 5,6, 7a, and 8 as shown in this excerpt from ChartNo. 1.

Schematic Layout of a Nautical ChartTo begin, it is useful to examine the sche-

matic layout of the nautical chart and to reviewthe overall format, including the textual mate-rial given in the chart. According to the DeskReference Guide,

�The chart format is the general plan oforganization or arrangement of a nauti-cal chart including the layout of the mar-gin notes, border, title block, and insets.�

Figure 2�2 presents the overall format of anautical chart, and figure 2�3 provides addi-tional explanatory information. The most im-portant items shown in figures 2�2 and 2�3 aresummarized in this chapter.

Number, Title, and Marginal Notes (A)Item 1 in figure 2�2 is the chart number (412

in this illustration) in the (U.S.) National ChartSeries, and item 3 is the corresponding chartnumber in the International Chart Series (ifany). The system used for charts produced byboth NOAA and NIMA assigns numbers tocharts based upon the scale and the geographicarea of coverage of the chart. One- to five-digitchart numbers are used. Details of the number-ing convention can be found in several sources(e.g., Bowditch). For the most part, mariners us-ing NOAA charts will be concerned with five-digit


Fig. 2-1. Schematic Layout of Chart No. 1

Schematic Layout of Chart 1

®--@--

K t

®

Rocks, Wrecks, Obstructions I

CD Wrecks Supplementary national symbolS:

Plane of Reference for Depths --> H

43.1[ I .. [ [

Subm piles Subm piles Slumps of posts or ()Obstn o. _______ ~

St~es. Perches pifes. lully submerged T"\ r

Subm piling

1 ) 1 1 ® ® ® ® ®

®

CD

®

®

@

Sec tion.

Section designation

Subsection

Reference to "Supplementary notionol sym bols" at the end of each section

Cross reference 10 terms in other sections

Column 1: Numbering following the New "Standard List of Symbols, A bbreviations, ond Terms" of the IHO

Column 2' Representation used on charts produced by the No /ionol Ocean Service (NOS). In cerlain instances, the represenrotion is clarified by 0 lobel on the chart

Column 3: Representation used on charts produced by the Oefense Mopping Agency (OMA). In certain instan ces, the representation is clorified by 0 label on the chart

Note When the NOS ond DMA symbols ore identical. Column 2 and Column 3 ore combined to show only one set of symbols

® Column 4: Descoption of symbol, term, or abbreviation

® Column 5: Represen tation following the "Chart Specifications ofma IHO "

@ Column 6: Representation of symbols that moy appear on DMA reproductions of foreign Chorts,

a

I

r f}

1 @)


Fig. 2–2. Schematic Layout of a Nautical Chart

A Chart Number, Title, Marginal Notes

o pajupdJaAO ~)-ueJOl G) (;Lv 0 009.iNI

104

~,

:;:; ~

~

@ ~ a: <C ::r: ()

m z

~

9 ~

O

g Unimak Pass " 1 12500

~ 53°51'OO"N

~ 5th Ed May 17/89 •

1 412 2 Loran·C Overprinted

Schematic layout of a chart (reduced in size)

DEPTHS IN METERS Nautical Chart Catalog N03 Panel I,M

Submarine Operating Area 207.640 (see note A )

/ /

/

®

/ /

104

/ /

/

Source Inset

54°56'OO"N

INTERNATIONAL

CHART 8ERI ES

UN ITED 8T ATES

ALA8KA- SOUTH COAST

Q COOK INLET Mercator Projection

~ Scale 1:100,000 at Lat 54°00'

Authorities

Note A

Pipelines @ ~~===~=

Caution

@

§ z Cl Q.

~ o z

g@ ~ m <C

(740,9 x 1103,9 mm) ~

INT 500 ® 412 <D


Source: Chart No. 1

Fig. 2–3. Items of Interest in Figure 2–2

A Chart Number, Title, Marginal Notes

Magnetic Features - B Tidal Data - H Decca, Loran-C, Omega _ S

Chart number in national chart series

CD Identification of a latticed chart (if any):

D forDecca Le for Loran-C Om forOmega

® Chart number in international chart series (if any)

® Publication note (imprint)

0 Stock number

® Edition note. In the example: Fifth edition published in May, 1989

® Source data diagram (if any). For attention to navigators: use caution where surveys are inadequate

0 Dimensions of inner borders

® Corner co-ordinates

® Charttitie } May be quoted when ordering a chart, in addition to chart number

@ Explanatory notes on chart construction, etc. To be read before using chart

® Seals: In the example, the national and International Hydrographic Organization seals show that this national chart is also an international

one. Purely national charts have the national seal only. Reproductions of charts of other nations (facsimile) have the seals of the original producer (left), publisher (center) and the IHO (right)

@ Projection and scale of chart at stated latitude. The scale is precisely as stated only at the latitude quoted

@ Linear scale on large-scale charts

@ Reference to a larger-scale chart

@ Cautionary notes (if any). Information on particular features, to be read before using chart

@) Reference to an adjoining chart of similar scale

@


chart identification numbers, which are drawnto a scale (see below) of 1:2,000,000 and larger.Chart numbers and their respective areas ofcoverage are presented in the nautical chartcatalog.

Latticed Charts (A)Item 2 in figure 2�2 indicates whether or not

a navigational lattice is overprinted on the chartand, if so, the type of lattice. For example, thelegend �LORAN�C OVERPRINTED� informs themariner that Loran�C TD data are superim-posed on the chart, the legend �D� that Deccainformation is included, and the legend�OMEGA OVERPRINTED� indicates thatOmega information is provided.

Although Decca and Omega navigation sys-tems are used extensively in other parts of theworld, Loran�C is of particular importance tomariners in U.S. waters. In view of the impor-tance of this system, many NOAA charts are over-printed with Loran�C TD data. Most modernLoran�C receivers are able to convert from TDsto latitude and longitude, but use of TDs is stillrecommended for highest accuracy (Loran�C UserHandbook) so a TD lattice is handy.

Nautical charts overprinted with a Loran�Clattice are identified in the nautical chart cata-log with the letter �C� enclosed with a circle infront of the chart number. Loran�C TDs are usu-ally provided on charts with 1:80,000 scale (seebelow) and smaller upon request of the USCG.Loran�C lattices are not shown on harbor or har-bor entrance charts at scales of 1:50,000 or largerand over most inshore areas or inland waters be-cause the navigational accuracy is adversely im-pacted by interference caused by land and/orbuilding structures.

Edition (A)The chart edition, shown as item 6 in figure

2�2, is one of the most important items of infor-mation given on the chart. The original date ofissue (not shown in figure 2�2) of a new chart isprinted at the top center margin. The edition

number (e.g., 5th ed. May 17/89 in figure 2�2) isprinted in the lower left-hand corner of the chart.New editions are published when, at the time ofprinting, the corrections from previous editionsare too numerous or too extensive to be reportedin the NM. Criteria for allocation of survey andchart compilation effort are given in table 2�1. Anew chart edition supersedes all earlier editions.The date shown is the same as that of the latestNM to which the chart has been corrected. In thisillustration, the 5th edition has been correctedthrough May 17, 1989. (Mariners sometimes over-look this important point, charts are correctedto the date shown, not to the date of purchase.Therefore, it is generally necessary to make cor-rections on a newly purchased chart.) A revisedprint published by NOAA may contain correctionswhich have been published in NM but does notsupersede the current edition of the chart. Thedate of the revision is shown to the right of theedition date. Thus, for example, 5th ed. May 17/89; Revised June 20/94, indicates that this chartwas revised in June 1994. A reprint, issued to re-place depleted stocks, is an exact duplicate of thecurrent issue with no changes in printing or pub-lication dates.

A study by the NRC, indicated that nominalprint cycles for NOAA charts range from 6 monthsto 12 years. In practice, new editions are initi-ated by the cumulative number of chart correc-tions, significant format or regulation changes,new basic data (e.g., survey data), low shelf stock,and available resources. Not all chart correctionsare critical; critical chart corrections includechanges in aid to navigation, obstructions, shoal-ing, and certain cultural and facility changes.According to NRC, 30 to 70 changes trigger a newedition.

Reconstructed, Provisional, andPreliminary Charts

Three other types of charts, reconstructedcharts, provisional charts, and preliminarycharts, are worthy of mention. According to theNautical Chart Manual:


� A reconstructed chart, is one that iscompletely recompiled on a new pro-jection. This is issued when the accu-mulation of new information is suffi-ciently extensive to affect most of anexisting chart, or if there are changesto the chart limits, or the chart is pro-duced using computer supported com-pilation and scribing techniques. A re-constructed chart is issued as a newedition.

Chart reconstruction is used to improve thequality of the chart and to incorporate any newsymbols and conventions developed over theyears. Changes in type style, particular symbols,and cartographic philosophy accumulate andevolve over the years with the result that oldercharts contain a mixture of type styles and mayinclude outdated symbols (e.g., symbolized depthcurves rather than labeled solid lines, excessive

use of road symbols rather than urban tint, etc.)and conventions. Moreover, the chart reproduc-tion process may cause a gradual deteriorationof the image (e.g., line thickening, symbols becom-ing less distinct, etc.) to the point that certainsymbols are difficult to recognize. When a chartis reconstructed, the symbology and chart con-ventions are updated along with the necessaryrevisions (e.g., relocated buoys, new wrecks,shoaling, etc.) typically noted in the NM or theLNM.

� A provisional chart is a special chartfor which there is an urgent need. Thechart is labeled �PROVISIONALCHART� in the upper and lower mar-gin or at a prominent location insidethe upper and lower border.

� A preliminary chart is one for whichthere is an urgent requirement that cov-

Table 2-1. Criteria Used to Set Priorities for Survey and Chart Compilation Effort

1. What is the cumulative number of NM or LNM corrections to the present edition?

2. How safe (or hazardous) to navigation is the area?

3. What type of craft frequent the area?

4. What is the volume of traffic in the area?

5. What resources are available for field surveys?

6. Where are the field resources and when can they be made available?

7. Which supporting data (e.g., tide, photogrammetry, geodesy) can be supplied?

8. What are the weather conditions in the area?

9. What comments have been received from the field regarding the adequacy of present charts?

10. What production resources are available to translate field data to charts and for subsequentchart compilation?

Source: Adapted with minor modification from the Nautical Chart Manual.


ers a region where some or all of thesurvey data fail to meet modern stan-dards. Survey deficiencies might in-clude small scale, outmoded or non-standard survey techniques, obsolete,unprocessed, or unapproved data, orother factors which cause the surveydata to be below customary standardsfor the scale of the chart. Not all pre-liminary charts are published in fullcolor. Additionally, the source diagram(see Chapter 4) alerts the mariner tothe provisional nature of the data, anda separate warning note is included.An illustrative warning note is shownbelow,

WARNINGPRELIMINARY CHART

�All of the data on this preliminary chart is

considered to be of marginal quality for mod-ern charts. Many of the depths were taken by

leadline in the early 1900s, so uncharted shoals

are likely in this area. Navigators should usethis chart with extreme caution and report

discrepancies or hazards to��

From the above, it is clear that preliminary chartsshould be used with particular care. However, thefact that the chart may include some data of mar-ginal quality does not mean that all data are sus-pect. If the preliminary chart has a source diagram(see Chapter 4), this diagram should be consultedto determine which areas of the chart may con-tain data of marginal or unverified quality. Mari-ners may be able to select routes which avoid theseareas. Alternatively, the mariner might choose agreater �safety margin� (e.g., depth allowance) inselecting routes, navigate with especial vigilance,navigate at reduced vessel speeds, and employother appropriate measures to reduce risk.

�Importance of Current and CorrectedCharts

Coote recounts one opinion on the use of cur-rent charts:

�In 1950 I joined Fandango for the Santender

Race returning via a race to Belle Ile and cruising

home� I looked over the charts [provided by theowner] and found that they had all been

bought� in June 1934. The suggestion that six-teen years and a World War might have outdated

some of the musty old charts was brushed

aside� by the owner [with the statement] �I be-lieve that the rocks don�t move, so what�s the mat-

ter with you�.�

This idiosyncratic view is colorful but fool-hardy; most mariners agree that it is essential touse the current edition/revision of the chart, up-dated to include all corrections given in the NMor LNM. Use of obsolete editions for navigationcould be dangerous; buoys are moved, otherATONs may have changed location or character-istics, new hazards (e.g., obstructions, wrecks) mayhave been identified, natural changes to hydrog-raphy may have occurred, and areas and limits(see Chapter 7) may have been changed. Indeed,as noted above, the accumulated number of chartcorrections is one of the principal determinants ofNOAA�s decision to prepare a new edition.

If prudence alone is not sufficient motiva-tion to ensure that a vessel is equipped withappropriate and corrected charts, marinersshould be aware that carriage of such charts isa legal requirement for certain classes of ves-sels. According to 33 Code of Federal Regula-tions (CFR) Part 164, self-propelled vessels of1,600 or more gross tons (when operating in thenavigable waters of the United States exceptthe St. Lawrence Seaway) are obligated (Sec-tion 164.33(a), et seq.) to carry (among otherthings) corrected marine charts of the areawhich are of a large enough scale and haveenough detail to make safe navigation of thearea possible.


The NOAA publication, Dates of Latest Edi-tions (issued quarterly), provides a list of the cur-rent editions of each chart. Techniques for mak-ing chart corrections are discussed in severalsources (e.g., Bowditch, Farrell, Maloney,Markel).

Source Diagram (A)A source diagram (item 7 in figure 2�2) indi-

cates the scale and date of hydrographic surveysupon which the nautical chart is based. Sourcediagrams and their utility are discussed in moredetail in Chapter 4.

Neat Line Dimensions (A)The size of a nautical chart is related to the

chart scale (see below) which is dependent uponthe amount of detail (geographic and cultural fea-tures, hydrography, etc.) that is charted to pro-vide a concise, legible, graphic representation ofthe necessary data. The chart dimensions alsoreflect the sizes of printing presses found innations around the world which reprint and re-issue NOAA charts. The internationally acceptedsize �A0� paper has outside dimensions of 841 mmx 1189 mm and is one of the standard sizes usedby NOAA.

The neat line is the inner border of the chart.The dimensions of the neat line (item 8 of figure2�2 or 740.9 mm x 1103.9 mm for this particularchart) are printed at the base of the chart. Neatline dimensions, in concert with the chart scale,enable calculation of the geographic area coveredby the chart.

Chart Title, Authorities Note, and Seal (A)Item 10 of figure 2�2 is the chart title (Cook

Inlet in this illustration). Although charts are gen-erally ordered by chart number, the chart titleserves as an additional identifier. The nauticalchart catalog shows the area covered by eachNOAA chart, and the corresponding chart num-ber and title. Chart titles cannot be used alone(in lieu of chart numbers) because many placenames (and chart names) are common through-

out the world. According to one source (Coote),for example, there is a St. John in Newfoundland,New Brunswick, Antigua, the Red Sea, Florida,the Virgin Islands, Liberia, and near Hong Kong!

Item 11 of figure 2�2 contains the AUTHORI-TIES note. This note identifies the sources of data(e.g., NOAA, USACE, U.S. Navy, etc.) used in thecompilation of the chart, explanatory notes onchart construction, and related material.

Item 12 is the chart seal. In the exampleshown in figure 2�2, the NOAA and IHO sealsshow this to be an international as well as na-tional chart. Purely national charts have the na-tional seal only. Reproductions of charts of othernations (facsimile) have the seals of the originalproducer (left), publisher (center), and IHO(right).

Projection and Scale (A)Item 13 in figure 2�2 (located just below the

chart title) identifies the type of chart projection(e.g., Mercator) and the chart scale. Projectionsand their relevance are discussed below.

�ProjectionsFrom earliest times, cartographers have been

faced with the theoretically impossible task of ac-curately representing a spheroid (the earth) on aflat plane, a task referred to as projection. As thescience of cartography evolved, numerous pro-jections were developed, each with advantagesand disadvantages. A complete discussion of thesevarious projections is beyond the scope of thismanual, but can be found in several of the refer-ences given at the end of this chapter (Air Navi-gation, Bowditch, Brown, Maloney, Naval Train-ing Command, Snyder, and Voxland).

For nautical charts of other than high-latitudeor polar regions, the Mercator projection is fa-vored. This is because meridians of longitude areparallel straight lines, as are parallels of latitude.These straight l ines intersect at r ightangles, making a convenient rectangulargrid. Directions and geographic coordinatesare easily read on this grid. A straight course line


(rhumb line or loxodromic curve) drawn on theMercator chart can actually be run; the rhumb linetrack will pass all features along that line exactlyas they are charted. This is a great advantage incoastal navigation because the straight line rep-resents a planned course and readily indicates thedistance at which dangers will be passed abeam ifthis course is maintained.

The rhumb line is not the shortest distancebetween two points (a great circle), and either cal-culation or an auxiliary chart is required to deter-mine great circle courses if a Mercator chart isused. However, the difference in distance betweenthe rhumb line and the shorter great circle is verysmall for all but the longest voyages. Radio wavesand light travel along great circles, which meansthat radio bearings taken some distance from thetransmitter need to be corrected. Radio bearingcorrections are tabulated on some nautical chartsand can also be found in the U.S. Coast Pilot andother references (Bowditch).

In a more general context, the chief disadvan-tage of the Mercator projection is that it distortsthe relative size of land areas�particularly forland masses located near the poles�other projec-tions are superior in this regard. Indeed, one au-thor (Monmonier) has argued (presumably tongue-in-cheek) that the Mercator projection has servedthe aims of political propagandists seeking to mag-nify the Communist threat, because this projec-tion exaggerates the relative size of the former So-viet Union relative to countries situated at lowerlatitudes. (One can only marvel at the political pre-science of Gerhard Mercator in anticipating thisapplication when he developed the projection inthe year 1569!) Whatever its other merits or faults,the utility and convenience of the Mercator pro-jection for most marine navigation applications areunequalled.

For this reason, nearly all NOAA nauticalcharts are based upon the Mercator projection. Thepolyconic projection is used on some NOAA GreatLakes charts, but these charts are being convertedto Mercator projections as resources permit.

Relevant attributes of Mercator and polyconiccharts are summarized in table 2�2. As a practical

matter, differences between these projections areonly apparent on small-scale charts (see below).On large-scale charts, virtually identical plottingtechniques are used.

The chief differences between small-scale Mer-cator and polyconic charts are:

� Distance is most accurately measured ator near the mid-latitude of the course onthe Mercator chart. Distance scales (seebelow) are shown in nautical miles onMercator charts, and in statute miles onpolyconic Great Lakes charts.

� For all intents and purposes, great circlesplot as straight lines on the polyconicchart. However, true directions from anypoint on the polyconic chart should bemeasured from the nearest meridian ornearest compass rose (see below). Asnoted, great circles do not plot as straightlines on Mercator charts. Instead, greatcircle courses must be calculated (or readfrom a polyconic or Gnomonic projection)as a series of points and transferred tothe Mercator chart. Details of plottinggreat circle courses on Mercator chartsare given in the references (Bowditch,Maloney).

� True directions (rhumb lines) can be mea-sured with respect to any meridian or par-allel (or any compass rose) on the Merca-tor chart, although in practice the near-est compass rose is used if magneticcourses are desired, because the magneticvariation varies with location on thechart.

� Plotting geographic positions is some-what simpler on the Mercator chart, be-cause meridians and parallels intersectat right angles. Great Lakes polyconiccharts include a graphic plotting inter-polator for the most accurate measure-ments of latitude and longitude.


�Chart ScaleThe scale of the chart is the ratio of a given

distance on the chart to the actual distance thatit represents on the earth. Scale is expressedin various ways. The most common expressionis a simple ratio or fraction known as the rep-resentative fraction. For example, a scale of1:40,000 or 1/40,000 means that one unit (e.g.,one inch) on the chart represents 40,000 of thesame unit(s) on the surface of the earth. Thisscale is also termed the �natural� or �fractional�scale. A chart covering a relatively large areais called a �small-scale chart,� and one cover-ing a relatively small area is termed a �large-scale chart.� To remember the difference be-tween small scale and large scale, it is helpful

to think of a small-scale chart as presenting onlya small amount of detail and a large-scale chartas presenting a large amount of detail.

On a chart based upon the Mercator pro-jection (the type shown in figure 2�2), the scalevaries with the latitude. This variation is onlynoticeable on a chart covering a relatively largedistance in a north�south direction. On such achart, the scale at the latitude in question shouldbe used for measuring distances.

Table 2�3 provides relevant scale informa-tion for various scales used in the preparationof nautical charts. For each chart scale, table2�3 shows the number of nautical miles repre-sented by 1 inch in length and its reciprocal,the length of 1 nautical mile in inches. This table

Projection Type

Attribute Mercator Polyconic

Invented by:Gerard Mercator (the Latinized form ofDeCremer or Kremer) in 1569.

Ferdinand Hassler, first director of theCoast Survey (later U.S. Coast andGeodetic survey) about 1820.

Poles: Cannot be shown. Points.

Projection: Cylindrical. Series of cones.

Conformality: Conformal. No, but approximately so.

Distance Scale: Variable (measure at mid-latitude).True along the central meridian and alongeach parallel.

Distortion of Shapes and Areas: Increases away from equator.Free of distortion only along centralmeridian. Extensive distortion forsmall-scale charts.

Angle Between Parallels andMeridians:

90° Variable.

Appearance of Parallels: Parallel straight lines unequally spaced.Arcs of nonconcentric circles nearlyequally spaced.

Appearance of Meridians: Parallel straight lines equally spaced.Curved lines (nearly straight) convergingtowards the pole and concave to thecentral meridian.

Straight Line Crosses Meridians: Constant angle (rhumb line).Variable angle (approximately greatcircle).

Great Circle:Curved line (except at equator andMeridians).

Straight line (approximately)

Rhumb Line: Straight line Curved line

Used for:Nearly all marine navigation charts producedby NOAA.

Some Great Lakes charts; being replacedby Mercator as resources permit.

True Direction Measured at:Any place on chart; nearest compass rosemost convenient.

Nearest meridian or compass rose.

Table 2-2. Key Characteristics of Projections Used in NOAA Nautical Charts


Table 2–3. Relevant Scale Information

ChartScale 1

1 Inch inNautical Miles

1 NauticalMile in Inches

CoverageSquare NM1

Nautical Chart Type2

Conventional Small Craft

5,000 0.069 14.58 6 Harbor

10,000 0.137 7.29 24 1:50,000 and

20,000 0.274 3.65 96 larger 1:10,000 to

30,000 0.411 2.43 217 1:80,000

40,000 0.549 1.82 385

50,000 0.686 1.46 601

60,000 0.823 1.22 866 Coastal

70,000 0.960 1.04 1,179 1:50,000 to

80,000 1.097 0.91 1,540 1:150,000

90,000 1.234 0.81 1,949

100,000 1.371 0.73 2,406

150,000 2.057 0.49 5,413

200,000 2.743 0.36 9,623

300,000 4.114 0.24 21,651 General

400,000 5.486 0.18 38,491 1:150,000 to

500,000 6.857 0.15 60,142 1:600,000

600,000 8.229 0.12 86,605

700,000 9.600 0.10 117,879

800,000 10.972 0.09 153,964 Sailing

900,000 12.343 0.08 194,861 1:600,000 and

1,000,000 13.715 0.07 240,569 smaller

2,000,000 27.430 0.04 962,274

3,500,000 48.002 0.02 2,946,965 International

10,000,000 137.149 0.01 24,056,854

Notes:1 Assumes standard neat line size of 750 mm x 1,100 mm for AO paper.2 ICW charts are at a scale of 1:40,000.


also shows the area covered (in square nauticalmiles) by the chart, assuming neat line dimensionsof 750 mm x 1,100 mm (one of the standard chartsizes). Thus, for example, on a chart with a scale of1:10,000 (a large-scale chart), the area covered bythe chart is approximately 24 square nautical miles,1 inch on the chart is approximately equal to 0.14nautical miles, and 1 nautical mile is approximately7.3 inches in length.

�Chart TypesNo one chart scale is adequate to serve all pur-

poses. Nautical charts vary in scale with the impor-tance of the geographic area, the purpose for whichthe chart is designed, and the necessity for clearlyshowing all dangers within that area. NOAA chartsinclude small-craft charts, conventional charts,ICW, and marine facilities charts.

Small-craft charts, identified by the letters �SC�in the nautical chart catalog, are described below:

� Small-craft charts, published at scalesranging from 1:10,000 to 1:80,000, are de-signed for easy reference and plotting inlimited spaces. Although normally usedby operators of small craft, these chartsprovide the only chart coverage for allother marine users in some areas. Thesecharts include the items normally depictedon other nautical charts together with de-tails of special interest to small-craft op-erators, such as enlargements of harbors;tide, current, and weather data; rules-of-the-road information; locations of marinefacilities and anchorages; courses and dis-tances. Types of small-craft charts include:folio charts (consisting of two to foursheets printed front and back, folded, andbound in a protective cardboard jacket);area charts (versions of conventionalcharts overprinted with additional small-craft information); route charts (publishedin a single long, narrow sheet printedfront and back and folded); modified routecharts; recreational charts; and canoecharts (a chart series of the Minnesota�

Ontario border lakes providing informa-tion relevant to those who use canoes, kay-aks, and similar craft).

Conventional charts are flat (rather than folded)and depict the nature and shape of the coast (seeChapter 3), depth of the water (see Chapter 4), gen-eral configuration and character of the bottom (seeChapter 4), prominent landmarks (see Chapter 6),port facilities (see Chapter 3), cultural details,dredged channels, ATONs (see Chapter 5), marinehazards, magnetics (described below), areas and lim-its (see Chapter 7), and seaward boundaries (seeChapter 7). The five classifications of conventionalnautical charts include:

� International charts (such as that illus-trated in figure 2�2) include a series offive small-scale charts covering the North-eastern Pacific Ocean and the Bering Seaat scales of 1:3,500,000 or 1:10,000,000 com-piled to internationally standardized car-tographic specifications. The navigationalinformation presented on these charts in-cludes depth curves, soundings, nauticalsymbols, and related data.

� Sailing charts, published at scales smallerthan 1:600,000, are intended for planningvoyages and for fixing the mariner�s posi-tion as the coast is approached from theopen ocean or for sailing along the coastbetween distant ports. The shoreline andtopography are generalized, and only off-shore soundings, principal navigationallights and buoys, and landmarks visibleat considerable distances are shown. Fig-ure 2�4 contains an excerpt from NOSChart No. 13003 (Cape Sable to CapeHatteras). This sailing chart is drawn to ascale of 1:1,200,000. In the right-hand cor-ner, some depth and ATON informationis depicted at the entrance to the Dela-ware Bay. No soundings, depth contours(see Chapter 4), or ATONs (see Chapter5) are given for the Chesapeake Bay, and


the city of Annapolis is depicted with onlya city symbol (see Chapter 7).

� General charts, published at scales rang-ing from 1:150,000 to 1:600,000, are in-tended for coastal navigation when acourse is well offshore but can be fixedby landmarks, lights, buoys, and charac-teristic soundings. Figure 2�5 containsan excerpt from NOS Chart No. 12260(Chesapeake Bay, Northern Part) show-ing a portion of the area covered in fig-ure 2�4. This general chart is drawn to ascale of 1:197,250. Soundings and ATONsin the Chesapeake Bay are shown, butAnnapolis is still depicted with only acity symbol, and very little detail is pre-sented in the vicinity of the Severn River.

� Coast charts, published at scales rang-ing from 1:50,000 to 1:150,000, are in-tended for nearshore navigation, enter-ing or leaving bays and harbors, and innavigating the larger inland waterways.Some coast charts omit detail in areasthat are covered by larger scale charts.For example (Chapman), NarragansettBay appears on NOS Chart 13218, butno hydrography, ATONs, etc., are de-picted. A small note refers the user to alarger scale chart. Figure 2�6 containsan excerpt from NOS Chart No. 12270(Eastern Bay and South River) depict-ing a portion of the area covered in thepreceding two figures. This chart isdrawn to a scale of 1:40,000, slightly largerthan a coast chart scale. Much more de-tail is presented on this chart. Citystreets, landmarks for position fixing,ATONs, soundings, and some harbordetail (e.g., piers, etc.) are clearly shown.

� Harbor charts, published at scales of1:50,000 and larger, are intended for navi-gating in harbors and smaller waterwaysand for anchorage. Harbor charts presentmore numerous soundings than are

shown on smaller scale charts and allATONs to maximize the accuracy ofpositions determined from plotted bear-ings. Figure 2�7 contains an excerpt fromNOS Chart No. 12283 (Annapolis Har-bor). This harbor chart is drawn to a scaleof 1:10,000. Individual buildings at theU.S. Naval Academy are shown as aredetails important to the mariner intend-ing to anchor in this area.

NOAA publishes ICW (inside route) charts ata scale of 1:40,000, which depict the inside routefrom Miami, FL, to Key West, FL, and from Tampa,FL, to Anclote Anchorage, FL.

Finally, NOAA publishes marine facilitiescharts. According to the Nautical Chart Manual,

[Marine facilities charts] �are conventionalcharts with small-craft marine facility in-formation overprinted on the chart and pre-sented in tabular form on the back. Theseare produced for major port areas wherefacility information for a wide area, suchas Narragansett Bay or Galveston harbor,is useful for the mariner.�

Marine facility charts are identified with theletters �MF� in the nautical chart catalog.

�A Mix of Charts NecessaryThe prudent navigator carries a mix of sailing

or general charts for overall voyage planning (if along distance voyage is contemplated), coast chartsfor actual use (e.g., intended tracks and DR plots)for the longer runs, and harbor charts for enteringports and trips up smaller rivers and creeks. Forexample, on a hypothetical voyage from Bermudato Annapolis, sailing and general charts would beused for offshore navigation, coast charts for thetrip up the Delaware Bay, through the C & D Ca-nal (although a large-scale chart of this canal ispublished), and down the Chesapeake Bay, andthe Annapolis Harbor chart for final approach andanchoring or docking. Continuing the example(Chapman), the best overall route up or down theChesapeake Bay is more easily plotted on two


Fig. 2–4. Excerpt from NOS Chart No. 13003(Cape Sable to Cape Hatteras)Drawn to a Scale of 1:1,200,000

general charts (NOS Charts 12220 and 12260),rather than on a series of five coast charts (NOSCharts 12221 to 12273) covering the same area.The coast and harbor charts are appropriate forthe actual trip.

As a general matter, the mariner is well ad-vised to use the largest scale chart of the area, asthis chart presents the greatest amount of de-tail. Many mariners carry harbor charts for otherharbors along the intended route as insuranceagainst the possibility that mechanical malfunc-tions, weather, fuel shortages, medical emergen-cies, or other unforeseen events make a diver-

sion to an alternate harbor advisable (Blewitt).Failure to carry sufficient charts to accommo-

date possible diversions can have serious conse-quences from both safety and legal standpoints,as numerous case studies of commercial vesselstrandings (Cahill) illustrate. In retrospect, it isvirtually impossible to justify the loss of a multi-million dollar tanker (or even a $50,000 cabincruiser) for the lack of a $14 chart! Although today'scivil penalties for a lack of prudence are less dra-conian than that listed in the opening quotation ofthis chapter, these are harsh enough to commandattention.


Fig. 2–5. Excerpt from NOS Chart No. 12260(Chesapeake Bay, Northern Part)

Drawn to a Scale of 1:197,250

A Brief Aside, Chart Storage and Care�Rollers versus Folders

As noted, conventional charts are sold as flatsheets, and typically shipped rolled in cardboardtubes, whereas small-craft charts are prefoldedto simplify stowage problems on small craft.Most mariners would agree that, ideally, con-ventional charts should be stored flat�in adraftsman's cabinet�provided adequate spaceexists. However, many vessels (and, indeed,most recreational vessels) do not have sufficientspace to accommodate flat storage of conven-tional charts.

There is no general consensus on how bestto store conventional charts in cramped quar-ters. Rather, the world of navigators (or, at least,the world of navigation textbook writers) ap-pears to be fundamentally divided on whetherto roll or fold these charts. �Rollers� (seeChapman, Graves) argue that conventionalcharts should be rolled if possible, claiming thatthe disadvantage of the ends curling is more thanoutweighed by the longer life of a chart if it isnot creased. �Folders� (Campbell) argue that itis difficult to plot on a rolled chart and offer nu-merous suggestions on how best to fold charts


Fig. 2–6. Excerpt from NOS Chart No. 12270(Eastern Bay and South River)Drawn to a Scale of 1:40,000

(e.g., in four sections, each about the size of anaverage navigation desk on a yacht, with theprinted side facing out). In the end, this re-duces to a matter of personal preference.

If there is controversy between �rollers� and�folders,� there is unanimity that charts shouldbe stored in a convenient but dry area in thevessel. Damp storage areas often result in mil-dew damage, and water spray creates bubbles,folds, and resulting distortions when the chartfinally dries out. Durable as it is, the paper onwhich nautical charts are printed cannot standrepeated cycles of water spray, let alone waterimmersion.

Linear and Logarithmic Speed Scales (A)Item 14 on figure 2�2 is a linear scale, often

provided on chart insets (see below) and largerscale charts. The linear scale (also termed a barscale) is found on Mercator charts (or insets)with chart scale of 1:80,000 and larger (1:120,000and larger for polyconic projections). Bar scalesenable the user to measure distances (in nauti-cal miles, statute miles (on Great Lakes charts),yards, and meters) quickly with a pair of divid-ers. The linear scale is used in lieu of the lati-tude scale at the side of the chart. Figure 2�8(top) shows an example of a bar scale.

Logarithmic speed scales, shown in figure


Fig. 2–7. Excerpt from NOS Chart No. 12283(Annapolis Harbor)

Drawn to a Scale of 1:10,000

2�8 (bottom), are also printed on these charts.The logarithmic speed scale is an ingenious no-mograph to solve time-speed-distance (TSD)computations. It is used to calculate speed,based upon the distance and time run. To findthe speed, one point of a pair of dividers isplaced on the distance run (in any unit) andthe other on minutes run. Without changingthe divider spread, the right point of the di-vider is placed on the number 60; the left pointof the dividers will then indicate the speed inunits per hour. Thus, for example, if a vesseltravels 4 nautical miles in 15 minutes, the cal-culated speed is 16 knots.

Notes and CautionsItem 16 on figures 2�2 and 2�3 refers to

cautionary notes (if any) depicted on the nau-tical chart. These notes, which should be readbefore using the chart, present a variety of gen-eral and particular information. Specific notesand their meaning are discussed throughoutthis manual. Table 2�4 provides a sample ofnotes taken from various nautical charts whichillustrates the type of information provided.Notes may be located at or near the title blockas shown in figure 2�2, but may also be locatedanywhere on the chart where they do not ob-scure navigationally relevant data or information.


Chart Overlap, Insets, and RelatedMatters

There is an old military adage (Heinl) tothe effect that battle is a process which alwaystakes place at the junction of two maps. Manynavigators believe that this maxim appliesequally to nautical charts. Before a vesselcrosses from waters described by one chart tothose covered by another, it is necessary toextend the course to the adjoining chart. More-over, the course has to be selected so as tomaintain a safe distance from charted hazardsand take advantage of ATONs and landmarksdepicted on the adjoining chart. As the vesselcrosses into waters depicted on the adjoiningchart, the navigator must be able to plot fixesrapidly on the next chart in sequence. If elec-tronic fixes are available (e.g., from a GPS orLoran�C receiver), the fixes are easily plot-ted on the appropriate chart. However, if vi-sual bearings are used, plotting fixes may bemore difficult if the vessel�s position is near achart border.

�Measures to Minimize Confusion:The Chartmaker's Perspective

NOAA uses four methods to minimizeproblems associated with the transition fromone chart to another.

� First, nautical charts are sized andaligned (insofar as possible) to ensurethat dangerous passages are not lo-cated near the chart borders. Thislowers the likelihood of a vessel en-tering a hazardous area when it is nec-essary to shift from one chart to thenext.

� Second, nautical charts are deliber-ately drawn so as to overlap slightly.Adjoining charts of the same scale,particularly coastal charts, generallyhave an inch or two of overlappingcoverage. The amount of overlap var-ies from chart to chart and is suffi-cient to include enough commonprominent features, important aids tonavigation, etc., to facilitate the quicktransfer of a plotted course and posi-tion from one chart to the next in se-quence. The detail presented on over-lapping charts of the same scale isidentical or nearly so.

� Third, if (despite efficient locationand overlap) there are still importantfeatures located just outside the chartborder, a border break (sometimes

Fig. 2–8. Bar Scales and Logarithmic Speed Scales Shown onSelected Nautical Charts


CAUT IONTemporary changes or defects in aids to navigation are not indicated on this chart. See: Notice to Mariners.

During some months or when endangered by ice, certain aids to navigation are replaced by other types or removed. For details see U.S. Coast Guard Light List.

RACING BUOYSRacing buoys within the limits of this chart are not shown hereon. Information may be obtained from the U.S. Coast Guard District Offices as racing and other privately maintained buoys are not all

listed in the U.S. Coast Guard Light List.

NOT E B DANGER AREAArea is open to unrestricted surface navigation but all vessels are cautioned neither to anchor, dredge, trawl, lay cables, bottom, nor

conduct any other similar type of operation because of residual danger from mines on the bottom.

CAUTIONOnly marine radiobeacons have been

calibrated for s urface use. Limitations on the use of certain other radio signals as aids to marine navigation can be found in the U.S.

Coast Guard Light Lists and Defense Mapping Agency Publication 117.

RADAR REFL ECTORSRadar reflectors have been placed on

many floating aids to navigation. Individual radar reflector identification on

these aids has been omitted from this chart.

WARNINGThe prudent mariner will not rely solely

on any single aid to navigation, particularly on floating aids. See: U.S. Coast Guard Light List and U.S. Coast

Pilot for details.

CAUT IONImproved channels shown by broken lines are subject to shoaling, particularly at the

edges.

CAUT IONExtremely heavy tide rips and strong currents

may be encountered in the vicinity of the islands shown on this chart.

NOT E CStrong currents exist between buoys

creating hazardous navigating conditions. Use extreme caution

NOT E A Navigation regulations are published in Chapter 2, U.S. Coast Pilot . Additions or revisions to

Chapter 2 are published in the Notices to Mariners. Information concerning the regulations may be obtained at the Office of the Commander, Coast Guard District , , or at the Office of the

Division Engineer, Corps of Engineers in , . Refer to charted regulation section numbers.

CAUTIONBASCULE BRIDGE CL EAR ANCES

For bascule bridges, whose s pans do not open to a full upright or vertical position, unlimited vertical clearance is not available for the

entire charted horizontal clearance.

CAUTION FIS H TR AP ARE AS AND S TRUCT URES

Mariners are warned that numerous uncharted duck blinds and fishing structures, some submerged, may exist in the fish trap area. S uch

structures are not charted unless known to be permanent.

NOAA VHF - FM WEATHE R BROADCAS TST he National Weather Service stations listed below provide continuous marine weather

broadcasts. The range of reception is variable, but for most stations is usually 20 to 40 miles from the antenna site.

Table 2–4. Illustrations of Various Notes and CautionsFound on NOAA Charts


also called an extrusion, extension, orblister) is used. The border break, as thename implies, is an extension of thecharted area outside of the chart neatlines to depict particularly importantfeature(s). Figure 2�9 presents an ex-cerpt from NOS Chart No. 11445 (Sug-arloaf Key to Key West), an ICW chart,which includes a border break. Note inthe lower right-hand corner of this il-lustration that the American Shoallight is actually located outside thechart border. Because this light isdeemed important to navigation, a bor-der break is used to show it on thischart. Border breaks are also used toeliminate the need for printing an ad-ditional chart. For example, figure 2�10 contains an excerpt from NIMAChart No. 28160 (Tela to Pelican Keys).The border break in this metric chartavoids the necessity of printing anotherchart just to depict the small portionof the Bahia De Amatique (HondurasBay) near the Temash River.

� Fourth, notes (and sometimes dia-grams) are provided on the nauticalchart to identify the adjoining chart(s)so that the user can quickly identify theappropriate chart. This is done in vari-ous ways. For example, notes (e.g.,JOINS CHART 12214, if the adjoiningchart is to the same scale, or CONTIN-UED ON CHART 12311 if the adjoin-ing chart is of a different scale) printedin black italic capital letters outside theneat line of the nautical chart identifythe adjoining chart. Refer to item 17 infigure 2�2. (Cross-reference to joinpoints on small craft and ICW chartsis facilitated by a dashed magenta sec-tion line, e.g., line AP - - - AP in figure2�9, which is also displayed on the ad-joining chart.) In cases where a largerscale chart of the same area is avail-able a note (e.g., chart 12284) is printedin lower case italic magenta type at ornear the boundary of the larger scalechart on the smaller scale chart. (Hy-drographic detail may be suppressed

on the smaller scale chart in this case.)In some cases the larger scale informa-tion may be presented in an inset (see,for example, item 15 in figure 2�2), inwhich case the inset will be printedsomewhere on the chart so as not toobscure navigationally relevant infor-mation. Finally, chart outlines and dia-grams are also used to display largerscale overlapping or adjoining chartcoverage on smaller scale charts. Theintent is to provide the user with a com-plete reference to larger scale chartcoverage. This is done either by pro-viding an outline of boundaries of thelarger scale chart on the smaller scalechart (as shown by item 15 in figure 2�2) or by providing a convenient chartindex diagram which shows the avail-able larger scale charts. Figure 2�11contains a chart diagram found on NOSChart No. 12260 which shows theboundaries of the larger scale chartsavailable for this area.

�Measures to Minimize Confusion:The Navigator's Role

The navigator should also take steps tominimize any confusion that might occur whenshifting from one chart to another.

� First, the proper adjoining (or largerscale) chart should be selected from thestorage area so that it is readily at handwell before the chart is actually re-quired. This is particularly importantif the mariner is �single-handing� (trav-eling alone) or if the chart storage com-partment is located some distance fromthe helm or plotting area. Indeed, it isa good idea to lay out all the requiredcharts for a voyage prior to getting un-derway, labelling each with a remov-able gummed label with an attached se-quence number. This procedure notonly facilitates selection of the rightchart, but also ensures that any miss-ing charts are identified at the dock,rather than while underway. Fewthings are more frustrating than hav-ing to divert to an alternate harbor


This figure illustrates a border break to include an important light and the dashed magentasymbol (AP – – – AP) to cross-reference a position on the next chart. Note also the skewed

projection.

Fig. 2–9. Excerpt from NOS Chart No. 11445 (Sugarloaf Key to Key West)

26 2S

26

21

24 22

27 rlry 27

37 38 37

__ ------30 20 23 24 22

____ ~9 ~6 15 20

----@ ________ I JO

23 -----;;:~-----SSh

2S


The border breakon this metric chartavoids thenecessity ofprinting anotherchart to depict thesmall area to theleft.

Fig. 2–10. Excerpt from NIMA Chart No. 28162(Tela to Pelican Cays)


Fig. 2–11. Chart Diagram Found on NOS Chart

No. 12260Identifies Larger Scale Charts to be Used for

Navigation

because the required chart is notaboard! (The alternative of pressing onwithout the missing chart in hopes thatthe channel is well-marked is so haz-ardous as to be unthinkable.)

� Second, the vessel�s intended trackshould be plotted on the adjoining (orlarger scale) chart before this chart isrequired. The DR plot should be drawnin while underway, but the intendedtrack can be plotted beforehand.Where possible, the intended trackshould be laid out so as to minimize thenecessity for accurate navigation in theimmediate vicinity of a chart junction.

� Third, if using landmarks or ATONs for

position fixing, the navigator shouldplan ahead to avoid selecting objectsthat are not shown on the same chart.For example, visual bearings on two ob-jects not shown on the same chart can-not readily be plotted to obtain a fix.Alternatively, the navigator can desig-nate a checkpoint or waypoint that islocated in the overlap area common toboth charts. Arrival at the waypoint sig-nals the need to change charts. This isparticularly convenient if a naviga-tional receiver (e.g., GPS or Loran�C)with a waypoint alarm is used.

� Fourth, the navigator should fix the po-sition of the vessel more frequentlywhen in the vicinity of the chart junc-tion.


� Fifth, the navigator should be particu-larly alert to any change in scale when-ever shifting to another chart as, for ex-ample, when shifting from a coast chartto a harbor chart. Although adjoiningcharts are often drawn to the samescale, this is not always the case. More-over, larger scale charts and chart in-sets always involve a change in scale.Attention to scale changes is particu-larly important if an external distancescale (e.g., a paraline plotter) is used.These instruments often have severaldistance scales scribed along thestraight edge. It is a common error touse the wrong distance scale, particu-larly when transitioning to a chart witha different scale from that used previ-ously. Use of the wrong distance scaletranslates into an incorrect DR plotwith attendant hazards. To avoid thiserror, many navigators disregard thescribed distance scales on plotters andalways measure distances with divid-ers using the latitude scales or the lin-ear scale printed on the chart. (Sepa-rate latitude scales or linear scales arealways printed on insets of a differentscale.)

Navigators using commercial reproductions ofportions of NOAA charts, especially thoseprinted in relatively small booklets, soon learnthat chart changes are more frequent and thatit is often difficult to find the adjoining chart inthe booklet.

Latitude, Longitude, Regular, and SkewedProjections

Each nautical chart will have lines markingparallels of latitude and meridians of longitude.(In the Mercator projection, as shown in table2�2, latitudes are parallel straight lines, and me-ridians of longitude are likewise parallelstraight lines.) These are used to measure thegeographic location of any point on the chart interms of latitude and longitude. The latitudescale is also used to measure distance; 1 nauti-cal mile is equal to 1 minute of latitude. The in-terval between adjacent parallels and meridians

depends upon the scale of the chart.Latitude and longitude scales are marked

with degrees and minutes. NOAA charts with ascale larger than 1:50,000 subdivide minutes intoseconds or multiples of seconds. Small-scalecharts subdivide minutes into tenths, fifths, orhalves. Read these scales carefully. It is alsoimportant for the mariner to note the units oflatitude/longitude readout of an electronic navi-gation receiver (e.g., GPS or LORAN-C) as thesemay differ from those used on the chart. For ex-ample, most electronic receivers measure lati-tude or longitude to degrees, minutes, andtenths (or hundreths) of minutes, rather thandegrees, minutes, seconds.

Most conventional charts are oriented �northup� with latitude scales at the sides of the chartand longitude scales at the top and bottom. Someconventional charts and many small-craft chartsare printed as a skewed projection so as to makethe most efficient use of space. In these skewed(non-north up) projections, lines of latitude andlongitude are not parallel to the borders of thechart. A skewed projection is illustrated in fig-ure 2�9.

Depth Units and Vertical DatumThe units of depth (e.g., feet, fathoms, fath-

oms and feet, meters) employed on the chart areshown in the title block and in capital magentaletters at the top and bottom of the chart. Asdiscussed in Chapter 4, NOAA charts are nowpublished in both �traditional� (feet, fathoms,fathoms and feet) and metric units. In the fu-ture, charts with traditional units are being re-placed by those charted in metric units. Kalsoffers an interesting anecdote on misreadingdepth units:

�In Montreal I once conned the craftof a friend who had urgent business be-low. Avoiding the ship channel, I headedstraight for our destination over sound-ings of 2, 3, and 4 fathoms. [Note 1 fathomis 6 feet.] No problem; his schooner drewonly 5 feet. The river must have beenwell above datum level or I would haverun her hard aground. The soundingswere in feet!�


Not all such stories have such a happy end-ing. It is essential to check the depth units onthe chart. This is especially important duringthe present transition period from conventionalunits to metric units.

The chart note regarding depth units alsodefines the vertical datum (typically mean lowerlow water for soundings and mean high waterfor heights) used on the chart, as discussed inmore detail in Chapter 4.

To provide a ready source of unit conversioninformation, NOAA charts also include a depthconversion scale. This scale shows the correspon-dence between fathoms, feet, and meters. Fig-ure 2�12 illustrates the depth conversion scaledesigned for horizontal placement. A similarscale has been designed for vertical placement.These scales are typically placed near the chartborders.

Horizontal DatumThe horizontal datum is shown just below

the title block of the chart. The horizontaldatum is a set of constants specifying the coor-dinate system used for geodetic control, that is,for calculating coordinates of points on the earth.Different horizontal datums use different ellip-soids to represent the earth's shape. Prior towidespread use of satellite systems for survey-ing and navigation, most countries developed anellipsoid that fitted the curvature of the earthfor the particular areas charted. In consequence,numerous datums were employed because thedatum providing the best fit for one area mightnot provide the best fit for another.

Most NOAA charts are based upon the NorthAmerican Datum of 1983 (NAD 83), the currentstandard for U.S. nautical charts. This datum isquite close to the World Geodetic System of 1984

(WGS 84). Other datums presently used onNOAA charts include the:

� North American Datum of 1927

� North American Datum of 1902 (foundonly on some Great Lakes charts),

� Old Hawaiian Datum,

� Puerto Rico Datum,

� Local Astronomic Datums, and the

� Guam 1963 Datum.

With the exception of the charts of the Ha-waiian Islands and other western Pacific islands(which will be compiled on WGS 84) all newcharts and reconstructed NOAA charts arebased on NAD 83.

�Relevance of Horizontal DatumFor navigators using radar or visual means

for position fixing, the particular datum used ismerely an academic curiosity. However, forthose using electronic navigation systems, suchas GPS or LORAN-C, the chart datum is poten-tially more relevant. This is because themathematical conversion routines employed inthese receivers to convert the received signals(e.g., LORAN-C TDs) to latitude and longitudedepend upon the assumed datum. A shift fromone datum to another could shift the position ofthe apparent fix by an amount ranging frommeters to miles. One source (Brogden) notesthat, outside the United States, it is common-place to find differences of half a mile to a milebetween GPS fixes and a local chart.

Fig. 2–12. Depth Conversion Scale for Horizontal Placement


Most modern makes and models of GPS andLORAN-C receivers have the capability of shift-ing from one datum to another (Dahl, Brogden),often offering a wide selection (as many as 50 to100) of alternate datums. If the vessel's naviga-tion receiver is so equipped, it should be set tomatch the datum used on the nautical chart ofthe area.

Direction and Magnetics (B)True and magnetic information is provided

on nautical charts to enable mariners to mea-sure direction and determine magnetic courses.This information is provided in various ways.Latitude and longitude lines provide north�south and east�west orientation. The marinercan determine true direction from either paral-lels of latitude or meridians of longitude withthe aid of various commercially available courseplotters. True and magnetic directions are pro-vided with one or more compass roses (B70) lo-cated on the chart. Magnetic information is alsodisplayed by the use of isogonic (lines of equalmagnetic variation) lines (B71) shown on thechart.

�Compass Roses (B70)A compass rose, as illustrated in figure 2�13

(top), is placed on nautical charts to help mari-ners plot bearings and lay out courses. As a pointof interest, the use of the compass rose to indi-cate true and magnetic directions is a traditiondating back several centuries. As noted byBrown, �The earliest known rose to indicate com-pass variation appeared on a map in theCosmographiae Introductio of Apianus printedat Ingolstadt in 1529.�

On the modern nautical chart, the compassrose consists of two concentric graduated circles:

� The outer circle (true rose), graduatedin increments from 0° through 360°, isaligned with true north. (Dependingupon the scale of the chart, the incre-ments may be 1°, 2°, or 5°.) The starsymbol atop the 0° mark presumablydenotes Polaris, the north star.

� The inner circle (magnetic rose), alsograduated in increments of 1°, 2°, or 5°and labeled MAGNETIC, is alignedwith magnetic north. The arrow atopthe magnetic scale points to magneticnorth. A second set of graduationswithin the inner (magnetic rose) circleis graduated in the older 32-point sys-tem (1 point = 11.25°). Half points andquarter points are also given.

� Another label (e.g., VAR 4° 15'W (1985)ANNUAL DECREASE 8', in figure 2�13), shows the magnetic variation(4°15'W) for the charted area as of aspecified date (January 1, 1985), and theannual increase or decrease to permitadjustment to the current date. This isnecessary because magnetic variationis not constant, but rather changes dueto the fluctuations of the earth's mag-netic fields.

Use of the compass rose for measuringcourses or bearings is explained in numeroustexts (e.g., Bowditch, Dutton) and is not dis-cussed here. Compass roses are positioned on achart so as to be convenient to the most impor-tant navigational areas, and at sufficiently fre-quent intervals so that all water areas are withinthe reach of the parallel ruler. If the compassrose is positioned on a land area, some topo-graphic detail may be removed to reduce chartclutter. Compass roses are not placed in waterareas at the entrance to a harbor, at or near haz-ards to navigation in the water, nor do the gradu-ations obscure relevant soundings.

Compass roses are printed in magenta onall new charts and new editions. Some existingcharts, especially those with magenta Loran�Clines, have compass roses printed in black. Thesewill be converted to magenta when new editionsare published.

�Local Magnetic Disturbance NotesLocal magnetic disturbances, which may

cause substantial deflections of the compass,occur quite commonly in shallow water near


Fig. 2–13. Compass Rose (B70) andIsogonic Lines (B71)

Shown on Nautical Charts

70 Compass rose, normal pattern (smaller patterns at compass rose may be used)

Magnetic Variation (example): 4° 15' W 1985 (8' E) on magnetic north arrow means Magnetic Variation 4° 15' W in 1985, annual change 8' E (i. e. magnetic variation decreasing 8' annually).

71 Isogonic lines

Magnetic Variation Curves are for 1985 The Magnetic Variation is shown in degrees, followed by the letter Wor E, as appropriate,

at certain positions on the curves. The annual change is expressed in minutes with the letter Wor E and is given in brackets, immediately following the variation.


mountain masses. Notes, printed in magenta,alert the mariner to these areas wherever de-viations of 2° or more (3° in Alaska) exist. Hereare two examples:

LOCAL MAGNETIC DISTURBANCE

Differences from normal variation of asmuch as 5° have been observed inGastineau Channel in the vicinity of Lat.58°15'.

LOCAL MAGNETIC DISTURBANCE

Differences of 12° or more from normalvariation may be expected in X Channelin the vicinity of Z point.

If space constraints prevent inclusion of theentire note, the full note is placed elsewhere onthe chart and the following reference note (inmagenta) is placed in the area of the disturbance:

LOCAL MAGNETIC DISTURBANCE(SEE NOTE)

�Isogonic Lines (B 71)Magnetic variation is shown by isogonic lines

on smaller scale charts. Isogonic lines are linesconnecting points of equal magnetic variation.The line passing through points having zerovariation is termed the agonic line.

Isogonic lines are shown on those chartsdrawn to scale at which a variation of 1° willresult in a distance between adjacent lines ofless than 12 inches. Each isogonic line is labeledwith the amount and direction of variation, andthe date of the variation. As shown in the ex-ample given below, charts with isogonic linescarry a magenta note stating the name of themathematical model used for computation, theyear the model was computed, and the year thecharted isogonic lines represent.

MAGNETIC VARIATION

Magnetic variation curves are for 1992derived from 1990 World MagneticModel and accompanying secular change.If additional change is in the samedirection as variation it is additive andthe variation is increasing. If annualchange is opposite in direction to thevariation it is subtractive and the varia-tion is decreasing.

Additional InformationCertain charts (e.g., small-craft and marine

facilities charts) provide a variety of additionalrelevant information in the form of notes, tables,and pictures of harbors, landmarks, or ATONs.Examples of additional information found onsmall-craft charts include:

� A tide note (H 30) which provides in-formation on tide heights, and dailytide tables are often printed on thejacket of small-craft charts.

� Marine facility tabulations (U 32), suchas that illustrated in figure 2�14, pro-vide information on tides, depth, ser-vices, and supplies found at variouslocations shown on the chart.

� Several charts include additional tech-nical tables, such as a radio bearing con-version table, to correct measuredbearings to Mercator bearings, a tableof distances to the horizon as a func-tion of the height of eye of the observer,a conversion table from degrees to com-pass points and vice versa, or a tablefor determination of wind speed fromobserved sea conditions.

� Several charts provide tables of port-to-port distances which are useful forvoyage planning.


Fig. 2–14. Marine Facilities TabulationFound on NOS Chart 11451

(Miami, to Marathon and Florida Bay)

·. __ ~~~.~I_~~~·i\Ch 'v1Af1 I 8 E M C S F=L TSL Ft IN C Wl GH i EH I DG

H' ! 6 -t--_t-t_M-" ... +-",,30'--r_"_1-- -t-----t--j- __ .+---+-+_+ 14 I 1cI I I F C W! Gn _B~~ 14

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P-H-- 1A.8u:"AT[O "APPROACH-FEET(REPO~TED)" IS TH~ DfP"TH AVAILABLE FI10M THE NE-AREST NATURAL OR DREDGED CHANNEL TO THE FAC!lITY TH[ TAB,)LATFD ~PUMP!NG STATiON")$ DEF)NE~ AS FAG!; ITlES AVA)L4BLi:' ,"'OR PU.MPING OVT BOA; HOl.DJNG TANKS

P-I,S TABeJLATION WAS PRODUCED USING COMPUTER ASSISTED METHODS


Although this same information is availablein a variety of companion publications, such asthe U.S. Coast Pilot or the Tide Tables, recre-ational boaters typically appreciate its inclusionon the nautical chart (NRC). Interestingly, manyprofessional mariners, who normally have theseother reference publications, would prefer �lesscluttered� charts (NRC), an illustration of thetrade-offs made by NOAA in deciding what toinclude.

Lettering Styles(Vertical versus Slant Type)

Chart features depicted in vertical type in-clude the names of topographic features andfixed objects which extend above high water.Slant (italic) type is used for names of hydro-graphic features, including names of waterareas, underwater features, and floating aids.

Use of Color on ChartsColor is used on nautical charts to call the

mariner's attention to key features and to facili-tate chart interpretation. NOAA uses f ivecolors (some with different shades) to depictchart features and other information: black, blue,gold, green, and magenta. The general color con-ventions on NOAA charts are as follows:

� black is used for most symbols, printedinformation (e.g., notes, titles, certainLoran�C TDs, etc.), to outline shores,topographic features, and depth con-tours;

� blue (in one or more tints) is used todepict shallow water areas, the bound-aries of certain regulated areas (seeChapter 7), and Loran�C TDs;

� gold (buff) is used to show land areas,and a darker screened tint is used toshow built-up areas, such as cities (oncharts published by NIMA, land areasare shown in a screened black that ap-pears to be gray);

� green is used to depict areas that coverand uncover depending upon the stageof the tide (e.g., marches, mud flats,sand bars, etc.), another shade of greenis used to depict green buoys anddaybeacons;

� magenta is used to depict red buoys anddaybeacons, lighted buoys, and impor-tant caution and danger symbols, com-pass roses, and recommended course(if given), Loran�C TDs; and finally

� white (the natural color of the chartpaper) is used to depict deep-waterareas, dredged channels, etc.

Symbols and AbbreviationsAs noted, a standardized set of symbols is

used to represent the various features depictedon nautical charts. These symbols are shown inChart No. 1 and discussed throughout thismanual. Numerous standardized abbrevia-tions are used on nautical charts to conservespace. These abbreviations, together with oth-ers used in this manual, are shown in appen-dix B.

Use of ChartsThroughout this manual the proper use of

nautical charts is explored at length. Two con-cluding comments are relevant here.

First, the mariner should keep in mindthat, aesthetics aside, the modern-day nauti-cal chart is a working tool. In earlier times,charts were highly valuable documentsprinted on animal skins, parchment, and othervaluable materials. The navigator's determi-nations of course and distance measurements,plots of dead reckoning positions, fixes, etc.,were typically made on separate pieces ofpaper. Distances and courses (the sailings)were determined by calculation, not actualplotting. Technical progress and economies ofscale have changed the chart from an object ofveneration to a working tool. Intended tracks,


• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

�Part of the responsibility for the continuing ac-

curacy of charts lies with the user. If charts are to

remain reliable, they must be corrected as indicated

by the Notice to Mariners. In addition, the user's re-

ports of errors and changes and his suggestions often

are useful to the publishing agencies in correcting and

improving their charts. Navigators and maritime ac-

tivities have contributed much to the reliability and use-

fulness of the modern nautical chart. If a chart be-

comes wet, the expansion and subsequent shrinkage

when the chart dries are likely to cause distortion.�

Bowditch

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

DR plots, bearings, fixes, distance measure-ment, ranges of visibility of lights, etc., are nowplotted on the chart, rather than laborious cal-culation. So don't be afraid to use the chart, andannotate it appropriately for the voyages youplan to take.

Second, the chart should be studied carefullybefore it is actually put to use. The legendsshould be read, scale determined (particularlyif the scale changes from chart to chart), and allnotes and symbols read and understood. On anactual voyage, particularly in congested and po-tentially dangerous waters, there may be littletime to consult additional documents to deter-mine the significance of a particular chart sym-bol, note, or legends. The horizontal datumshould be noted and the GPS or LORAN-C re-

ceiver checked to ensure that this datum isbeing used. Latitude and longitude scalesshould be reviewed as these differ from chartto chart. Depth units should be checked and arealistic danger sounding selected (see Chap-ter 4) and marked on the chart. The navigatormight wish to annotate the chart with addi-tional relevant information, such as arcs of vis-ibility of lights, prominent ranges, landmarks,facilities, danger bearings, and other relevantinformation from the chart or other sourcessuch as the tide or tidal current tables, LightList, or U.S. Coast Pilot. As noted earlier, thecharts should be laid out and sequenced to en-sure that all necessary charts are aboard andthat they can be retrieved expeditiously andin the correct order.


ReferencesAdmiralty Charts and Publications. Sym-

bols and Abbreviations Used on AdmiraltyCharts, Chart 5011, Edition 1, HydrographicOffice, Taunton, Somerset, TA 1 2DN, UnitedKingdom, 1991.

Blewitt, M., Navigation for Yachtsmen, DavidMcKay Company, Inc., New York, NY, 1976.

Brogden, B., �Defining Terms, Since AllChart Datums Are Not Interchangeable, Elec-tronic Positions Should Be Used Carefully,�Ocean Voyager, 1994, pp. 16, et seq.

Brown, L. A., The Story of Maps, Dover Pub-lications, Inc., New York, NY, 1979.

Cahill, R. A., Strandings and Their Causes,Fairplay Publications, London, UK, 1985.

Campbell, S., The Yachting Book of Practi-cal Navigation, Dodd, Mead and Company,New York, NY, 1985.

Canadian Hydrographic Service. Chart No.1/Carte No. 1 Symbols Abbreviations Terms,Minister of Fisheries and Oceans Canada,January 1992.

Coote, J. O., Yacht Navigation�My Way, W.W. Norton & Company, New York, NY, 1987.

Dahl, B., The User's Guide to GPS, The Glo-bal Positioning System, Richardson's MarinePublishing, Evanston, IL, 1993.

Defense Mapping Agency, Hydrographic/Topographic Center. American Practical Navi-gator, An Epitome of Navigation (Bowditch),Publication No. 9, NIMA Stock No. NV PUB 9V1, Bethesda, MD, 1995.

Departments of the Air Force and theNavy. Air Navigation, AMF 51�40, NAVAIR00�80V�49, Washington, DC, 1983.

Eyges, L., The Practical Pilot, Coastal Naviga-tion by Eye, Intuition, and Common Sense, Inter-national Marine Publishing, Camden, ME, 1989.

Farrell, C., Fell�s Official Guide to SmallBoat Navigation, Frederick Fell Inc., NewYork, NY, 1962.

Graves, F., Piloting, International MarineCompany, Camden, ME, 1981.

Hobbs, R. R., Marine Navigation, Pilotingand Celestial and Electronic Navigation, ThirdEdition, Naval Institute Press, Annapolis, MD,1990.

Human Technology, Inc. Desk ReferenceGuide: Specifications Unit, Chart and Map,Feature: Format. Report developed for Na-t ional Ocean Service, Chart ing and Geo-detic Services, Marine Chart Branch, Un-der Contract OPM-85-77, McLean, VA, Oc-tober 1985.

��: Graphics.��: Specifications.

Heinl, R. D., Dictionary of Military and Na-val Quotations, Naval Institutes Press, An-napolis, MD, 1966.

Kals, W. S., Practical Navigation,Doubleday & Company, Garden City, NewYork, NY, 1972.

Larkin, F. J., Basic Coastal Navigation,Sheridan House, Dobbs Ferry, New York, NY,1993.

Maloney, E. S., Chapman Piloting, 60thEdition, Hearst Marine Books, New York, NY,1991.

��. Dutton�s Navigation and Piloting,Fourteenth Edition, Naval Institute Press, An-napolis, MD, 1985.

Markell, J., Coastal Navigation for theSmall Boat Sailor, Tab Books, Blue Ridge Sum-mit, PA, 1984.

Monmonier, M., How to Lie with Maps, TheUniversity of Chicago Press, Chicago, IL, 1991.


National Research Council. Charting aCourse Into the Digital Era, Guidance forNOAA's Nautical Charting Mission, NationalAcademy Press, Washington, DC 1994.

Naval Training Command. A NavigationCompendium, NAVTRA 10494�A, U. S. Gov-ernment Printing Office, Washington, DC,1972.

Schofield, B. B., Navigation and Direction,The Story of HMS Dryad, Kenneth Mason,Homewell, UK, 1977.

Snyder, J. P. and P. M. Voxland, An Albumof Map Projections, U.S. Geological Paper 1453,U.S. Government Printing Office, Washington,DC, 1989.

Toghill, J., Coastal Navigation, W. W.Norton & Company, New York, NY, 1987.

U.S. Department of Commerce, Coast andGeodetic Survey. Nautical Chart Manual, Vol-ume One: Policies and Procedures, Seventh Edi-tion, Washington, DC, 1992.

U.S. Department of Commerce, NationalOceanic and Atmospheric Administration,National Ocean Service, and Department ofDefense, National Imagery and MappingAgency. Chart No. 1 United States of AmericaNautical Chart Symbols Abbreviations andTerms, Ninth Edition, Washington, DC, Janu-ary 1990.

U.S. Department of Commerce, NationalOceanic and Atmospheric Administration, TheBoat Show Briefing Book, External and Coop-erative Affairs Group, Mapping and ChartingBranch, Riverdale, MD, 1993.

U.S. Department of Commerce, NationalOceanic and Atmospheric Administration,National Ocean Service. Dates of Latest Edi-t ions, Nautical Charts & Misc. Maps, Sil-ver Spring, MD, October 1, 1994 (issuedquarterly) .

U.S. Department of Transportation, UnitedStates Coast Guard, LORAN-C User Hand-book, COMDTPUB P16562.6, Washington, DC,1992.

Topography and Related Information 3-1

CHAPTER 3

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Fig. 3-4. Excerpt from NOS Chart No. 18650 (San Francisco Bay), showing contour lines on hill near Candlestick Park


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Fig. 3-5. Distance to the Visual Horizon

HE IGHT OF E YE (FT )

OBJECT HEIGHT (F T )

DIS

TAN

CE

(N

M)


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Table 3-1. Distance to the Visual Horizon (NM) as a Function of the Height of Eye (ft)and Object Height (ft)

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Fig. 3-7. Excerpt from Chart No. 1

17

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Fig. 3-8. Another excerpt from NOS Chart No. 18650 (San Francisco Bay),showing numerous small and large piers along the waterfront

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Fig. 3-9. Excerpt from Section D of Chart No. 1 Illustrating Various Bridge Symbols


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Hydrography and Related Information 4-1

CHAPTER 4

Hydrography andRelated Information

Introduction and OverviewThe scope of this chapter includes hy-

drography (e.g., depth curves, soundings,nature of the bottom) and various specifichazards to navigation. Hazards can be eithernatural (e.g., rocks, reefs, shoals, tide rips,breakers) or artificial (e.g., wrecks, marinestructures, unexploded ordnance, cable, andpipeline areas). This chapter provides essen-tial background (e.g., definitions, historicalasides), summarizes the utility of this infor-mation, describes the charting conventionsused to depict hydrographic information(e.g., symbols and notes), highlights possiblelimits to the accuracy of this information(some made explicit in chart information),identifies other relevant sources (e.g., theU.S. Coast Pilot, the Tide Tables and TidalCurrent Tables, NM, and LNM), and containspractical pointers on how hydrography andrelated information can be used by the pru-dent mariner.

In broad terms, the chapter addresses hy-drographic features (e.g., soundings, depthcurves, channels, nature of the bottom) andthe cartographic depiction of several specifichazards to navigation (e.g., rocks, shoals, ob-structions, wrecks). Because the scope of thismaterial is so broad and the information soimportant, this chapter is long and detailed.

Many specialized terms used in this chap-

ter are defined in the Glossary in appendix A.Names enclosed in parentheses (e.g.,Bowditch) denote references listed at the endof this chapter that contain additional relevantdetail or useful general discussions.

�A Brief Aside: Dual UnitsAs of this writing, NOAA is in the pro-

cess of converting charts from traditional or�English� units (e.g., feet, fathoms) to met-ric units (e.g., meters). The Metric Systemhas been established by the Metric Conver-sion Act of 1975 and the Omnibus Trade Actof 1988 as the preferred system of weightsand measures in the United States. For U.S.nautical charts, the conversion to metricunits is a multiyear effort with full imple-mentation expected after the year 2000. Ad-miralty charts wil l be ful ly converted tometric units by the year 2010 (Bunyon). Inthe interim, charts in both systems of unitswill be available, so this manual treats bothsystems. The changeover to metric units iscomplex for many reasons, but users shouldhave no difficulty converting from one sys-tem of units to the other. Illustrations pro-vided in conventional units (e.g., soundings)can be mentally converted to metric units(meters and tenths) so no particular empha-sis has been placed on the use of metric il-lustrations in this manual.

� � � � � � � � � � � � � � � � � � � � � �

�Any ship can be a survey ship,� once.�Richards

� � � � � � � � � � � � � � � � � � � � � �


Utility of Hydrographic and RelatedInformation

Approximately 71percent of the surface ofthe earth is covered with water (Kember), andit is reasonable to believe that (on an overallbasis) water would encompass at least this per-centage of the area of the average nauticalchart (excluding harbor charts). Regardless ofthe accuracy of this assertion, it is certainlytrue that the depiction of hydrographic andrelated information is one of the defining char-acteristics of the nautical chart as opposed tothe landbound map.

In a sense, any question relating to the util-ity of hydrographic and related informationon the nautical chart is almost rhetorical.Nonetheless, it is instructive to set forth someof the uses of hydrographic and related infor-mation. Table 4�1 outlines both general andspecific uses of this information to the mari-ner. Simply put, this information is essential

to effecting a safe and efficient voyage�de-termining a relatively direct course from ori-gin to destination while avoiding hazards tonavigation.

Depth information (particularly in areasof substantial gradient) can often be valuableas an aid in fixing the vessel�s position. Andfollowing a depth contour (using the vessel�sdepth sounder) can be a useful technique incircumstances of restricted visibility. Chartedislets (rocks which are above water) can alsobe used for position fixing�rather like a land-mark (see Chapter 6) in the water.

1 See chapter 7.

Specific Illustrations:

• To voyage expeditiously without running aground (e.g., depth information, limits to channels,presence of shoals, reefs, submerged rocks, etc.).

• To ascertain whether anchoring is possible (e.g., depth, type of bottom, absence of restrictions,absence of unexploded depth charges, etc.) or desirable (e.g., designated anchorage areas1) andaid in the determination of the proper amount of anchor line to deploy (depth) or even type ofanchor to deploy (type of bottom).

• To identify which slips/piers are suitable for berthing (depth, nearby hazards).

• To be used as an aid in fixing the vessel's position (e.g., depth curves, bare rocks, strandedwrecks, etc.).

• To facilitate tracking during times of reduced visibility and/or when operating in areas with fewATONs or distinguishing topography/landmarks (e.g., depth). For example, in waters with arelatively steep depth profile, a depth sounder can be used to track along a depth curve.

• To provide information relevant to fishing activities (e.g., locating wrecks or fish havens). Also, toavoid areas where fishing nets or other equipment might be damaged.

• To avoid possible hazards to operation (e.g., fish trap or stake areas, log booms, pilings, wrecks,deadheads, stumps, snags, tide rips, etc.).

• To identify areas of special interest to various user-community segments (e.g., drilling platforms,artificial islands, hunting and fishing structures, etc.).

Table 4-1. Uses of Hydrographic and Related Information

Some of the features normally classified ashazards to navigation, such as fish havens,wrecks, and offshore drilling platforms, areof interest to particular chart users. The rec-reational or charter fisherman, for example,is vitally interested in the accurate locationof fish havens and wrecks (where fish often


congregate). Vessels or aircraft that serviceoffshore rigs need to know where these arelocated�not to avoid them but to travel tothese structures.

Yet other features, such as foul areas,areas where unexploded depth charges lie,and cable or pipeline crossings do not neces-sarily present hazards to transiting vessels,but rather mark areas where certain activi-ties may be restricted or ill-advised. For ex-ample, foul grounds may snag fishing nets orlines, anchoring is prohibited in the vicinityof submerged pipelines and cables, and an-choring is unwise in areas where unexplodedordnance is reported.

Finally, the bottom characterist ics arerelevant for several reasons. Bottom samples,drawn with tallow attached to a leadline, wereused in bygone times as an aid in determiningthe vessel�s position (Cohen). Nowadays,knowledge of the nature of the bottom ischiefly important in selecting a suitable placeto anchor and the type of anchor to use (Hinz).

As noted above, hydrographic informationis first discussed, followed by specific hazards

to navigation.

Hydrographic InformationHydrographic information, as portrayed on

the nautical chart, consists of depth soundings,depth contours or curves, depth-dependent colordesignations (blue tints), notes showing the con-trolling depth of improved channels, and de-scriptions of the nature of the bottom. Taken to-gether, this information enables the marinerto navigate safely and efficiently.

�Common Plane of Reference and SurveyScales

Hydrographic surveys are the basic sourceof soundings and related information. Thesesurveys, conducted by NOAA and other ves-sels, utilize information derived from a wiredrag apparatus (earlier technology), echosounding, and side-scan sonar. Sounding dataderived from these surveys are adjusted to re-flect a common horizontal plane of reference,mean lower low water (MLLW), as shown infigure 4�1. By definition MLLW is an average(generally over a 19-year epoch) of all lowest

Fig. 4-1. Diagram taken from Chart No. 1 illustrating conventions used for charting soundings, dryingheights, charted clearance of bridges, and the charted height of lights. Soundings determined from

surveys are first reduced to depths relative to mean lower-low water before being charted. MLLW alsoserves as the reference plane for drying height.


water levels for tidal days.1 Viewed from thisperspective, charted soundings are conserva-tive, in the sense that depths are typicallygreater than shown by soundings data. Eventhough the datum is based on averages of lowwater (lower low water in cases where thereare two low-water periods in a day), the ac-tual water level at any time can be lower thanthis average�which means that the actualwater depth can be less than the charted depth.On days with spring tides (tides having agreater range than normal), prolonged windsfrom certain directions, or persistent ex-tremes of barometric pressure, the actualdepth of water can be less than the charteddepth.

The basic scale for hydrographic surveysperformed by NOAA is 1:20,000�other scalesare multiples or fractions of this basic scale.As noted in the NOS Hydrographic Manual,

�The criteria used for scale selec-tion are based on the area to be cov-ered and the amount of hydrographicdetail necessary to depict adequatelythe bottom topography and portray theleast depths over critical features. Acardinal rule of nautical chart construc-tion is data from a hydrographic sur-vey should always be plotted at a scaleratio larger than that of the chart to becompiled. The survey scale is generally

1In locations with two low tides each day, this is the average of the lower of the two.

The Rainier is one of the hydrographic survey ships in NOAA's fleet. Survey data are also provided byother government agencies and firms under contract to NOAA.


at least twice as large as that of the larg-est scale chart published or proposedfor the area� Inshore surveys, definedas those conducted adjacent to theshoreline and in general depths of 20fathoms or less shall be plotted atscales of 1:20,000 or larger . . . In con-trast, offshore surveys are those con-ducted in waters of general depths be-tween 20 and 110 fathoms not adjacentto the shoreline.

�Basic hydrographic and navigablearea surveys of all important harbors,anchorages, restricted navigable wa-terways, and areas where dangers tonavigation are numerous shall be plot-ted at scales of 1:10,000 or larger.�

Cartographers, therefore, always have hy-drographic information available at a largerscale than are plotted on the nautical chart(more below).

�Source DiagramsA source diagram is included in all new edi-

tions (after November 20, 1992) of NOAA nau-tical charts at a scale of 1:500,000 or larger. (Asource diagram is included on similar Admi-ralty charts.) It provides information on thesource, date, and scale of the survey(s) usedin the preparation of a given chart. The sourcediagram provides an indirect indication of thequality of the data (older surveys used lessmodern equipment, may not have been as com-plete, and the depth profile of the bottom mayhave altered over time as a result of suspen-sion and deposition processes). This informa-tion allows users to make their own judgmentsof the data�s fitness for a particular purpose.The date of the survey may prove useful inselecting a route�transiting areas more re-cently surveyed in preference to others.

Large-scale charts compiled exclusivelyfrom a single survey do not contain a sourcediagram. Instead, this information is providedin a parenthetical expression (e.g., from sur-veys of 1982 to 1984) to the AUTHORITIESnote shown on each chart.

Figure 4�2 provides an illustrative source

diagram, taken from NOS Chart No. 13218(Martha�s Vineyard to Block Island). TheQueen Elizabeth II (QE II) ran aground(Brogden, Sabellico, Walsh, Ocean Navigator)in August 1992 on an uncharted rock in area�d� (plotted with soundings from a 1939 sur-vey) on this source diagram. The QE II, draw-ing 32 feet, went aground in an area having ashoalest charted depth of 39 feet. A full dis-cussion of the incident is beyond the scope ofthis manual, but it does serve as a cautionarytale and illustrates the wisdom of providingan ample margin of safety beyond the mini-mum depth required to accommodate thevessel�s dynamic draft.

The master of the QE II might have se-lected a route which provided a greater mar-gin of safety had a source diagram been avail-able. Inspection of this source diagram and thechart itself indicates that, in general, the shal-lower areas have been the subject of more re-cent (and larger scale) surveys by NOAA.

SoundingsAs noted, the inclusion of individual sound-

ings is one of the ways in which hydrographicinformation is represented on the nauticalchart. Individual soundings are expressed inmeters and tenths (decimeters) on new charts,and in feet and fathoms on older charts, mea-sured relative to MLLW. The source of thesoundings data is the hydrographic survey(s)of the area to be charted.

As noted above, surveys are normally con-ducted at a scale larger than the largest scalechart of the area. Depicting all of the surveysoundings on the chart�particularly at asmaller scale�would be difficult or impos-sible. Recall all the other features, such asATONs, hazards, and areas and limits (Chap-ter 7) that compete for space on the nauticalchart (Kember). Even if physically possible toprepare, a plot showing all hydrographic sur-vey data would be very cluttered and difficultfor the mariner to interpret�at least for thewell-surveyed coastal areas. Figure 4�3 illus-trates the differences between detailed hydro-graphic survey soundings (on the left side) andthose generalized and plotted on a typical nau-tical chart (on the right side).


As a practical matter, therefore, the car-tographer is faced with the important task ofselecting a subset of the available soundingsfor depiction on the chart (e.g., Zoraster,Ekblom). The objectives of the selection pro-cess are to ensure that the overall presenta-tion of depth data is accurate, as complete asfeasible, and is easily understood by mariners.

�The Soundings Selection ChallengeTo explain the particular selection rules

and guidance followed by cartographers, it iswell to remember that the primary functionof soundings and depth curves on nauticalcharts is to present an accurate portrayal ofthe bottom configuration. Key bottom features

that are charted include shallow areas, shoals,banks, and bars, irregular bottoms, smoothbottoms, deeps, and navigable natural chan-nels and passages. These features are definedin table 4�2. (Additional material can be foundin appendix A.) Briefly, these features serve todefine preferred routes (e.g., navigable channelsor passages), areas to be avoided (e.g., shoals,ledges), opportunities for position fixing (e.g.,deeps, irregular bottoms), or other relevantdetail (e.g., smooth bottoms).

The aim of the selection process, therefore,is to reduce the total number of soundings (soas to improve chart clarity) yet still provide asufficient number of soundings to identify andlocate the features described in table 4-2. The

Fig. 4-2. Source diagram taken from NOS Chart No. 13218 (Martha's Vineyard to BlockIsland). The diagram provides an outline of the land areas and the areal limits of the

various surveys used in the preparation of the chart. The date, source, and scale of thesurvey are shown at the top of the source diagram.


selection process does not operate by merelydeleting a certain number of survey soundingse.g., by deleting every second point. Rather,the process takes cognizance of the informa-tion content of each sounding, and preferen-tially retains �significant� soundings. A suffi-cient sounding density is retained to depictnatural channels, shoals, or other hazardousareas to highlight these features for quick rec-ognition by the mariner. Additional (but fewer)supportive soundings are selected to completethe bottom description. The spacing of sound-ings on the nautical chart is also relevant. Fillsoundings (see below) over flat bottom areasare relatively widely spaced. Soundings inshoal areas are provided in greater density,which serves to draw the attention of themariner to these potentially dangerous areas(Magee).

In general, cartographers first selectsoundings from shoal areas and natural chan-nels and work toward deeper water so as toidentify all shoal areas that might impede sur-face navigation, provide information aboutnatural channels between or through shoalareas, and portray the configuration of thebottom (Nautical Chart Manual, Kember). Asof this writing, the selection of soundings isstill a manual process, although computermodels (Zoraster) show promise.

�Selection Criteria for Soundings to beCharted

The above discussion summarizes the ob-jectives and overall importance of the selec-tion of appropriate soundings for depiction onnautical charts. This section summarizes thespecific criteria and guidance used by cartog-raphers for selection of soundings.

These criteria, and supporting guidance,are summarized in table 4�3. In brief, the em-phasis is on selection of soundings whichpresent information on least depths, criticalsoundings, deep soundings, supportive sound-ings, and fill soundings. Additional specificguidance is also given in table 4�3 for selec-tion of channel range soundings, nonjunctionsoundings, changeable soundings, soundingsin slips and around piers, depths over rocks,areas where the survey has not been able todetect the bottom, and river depths.

Broadly, the criteria offered in table 4�3identify soundings to be emphasized (e.g.,least depths, critical soundings, deeps),soundings of lesser importance (e.g., support-ive soundings, fill soundings), and circum-stances where the depiction of soundings isill-advised (e.g., depiction of soundings inchangeable areas).

Skippers of recreational craft often expressSOUNDING DENSITY

HYDROGRAPHIC SURVEY CHART

Fig. 4-3. Differences between hydrographic survey information and that provided on atypical chart. The chart on the right is much easier to read, yet does not sacrifice any

information critical to navigation.


TABLE 4-2 Bottom Features Depicted on Nautical Charts

Shallow areas:Shallow areas are large expanses of shoals or of shallow water where the changes in depthare relatively slight. Some bays fed by river systems are shallow throughout.

Shoals, Banks, and Bars:Shoals are shallows that constitute offshore hazards to navigation. They are defined as havinga depth of 10 fathoms or less and may be composed of any material except rock or coral. Ashoal may be an isolated feature or part of a shoal area composed of two or more shoals. Abank is an area of relatively shallow water which is, however, of sufficient depth for safenavigation. Bars are ridges of sand or gravel, often at the mouth of a river, which may obstructnavigation. Note that shallow areas of rock and coral are charted as ledges and reefs andlabeled, rather than being delineated solely by depth indicators.

Irregular Bottoms:Irregular bottom areas may consist of shoals, shallows, passages, deeps, etc., and arecharacterized by relatively large and abrupt depth differences throughout the region.

Smooth Bottoms:Smooth bottom areas are expanses where variations in depth are gradual and are relativelysmall compared to the size and depth of the area as a whole. Smooth areas in relatively deepwater are the least important feature shown on charts. Generally, they pose no navigationalhazard. These are depicted to provide “bottom detail” to navigators, rather than to enhanceboater’s “safety.”

Navigable Channels and Passages:A channel or passage is a relatively deeper navigable route through an otherwise shallowarea. Natural channels or passages are important features which contribute to the naviga-tional value of a chart. Natural channels may constitute routes from deep water into shore orharbor areas, or routes between deep water areas through shoals or bordering shallow areas.

Deeps:Deeps are local deformations in the bottom configuration characterized by a significantincrease in depth when compared to the surrounding areas. The boundary of a deep is thezone which separates the deep area from the surrounding shallower water. The size of thezone depends on how well the deep can be distinguished from the surrounding area.

SOURCE: Nautical Chart Manual.

large commercial vessels draw much more.Super tankers, for example, draw 40 feet ormore (the ultra-large crude carrier, SeawiseGiant, built in 1979 reportedly draws almost100 feet!), and a submarine at periscope depthdraws 100 feet (submarines operate at depthsconsiderably greater). Second, operators of alltypes of vessels can use depth information asan aid in position fixing and for tracking alonga depth curve (see below).

puzzlement at some of the deeper soundingsincluded on the nautical chart. After all, mostrecreational power boats draw 4 feet or less,and most recreational sailboats probably draw6 feet or less. Why, they ask, include chartdepths much greater than this? There are sev-eral reasons for inclusion of deeper sound-ings�but two are particularly relevant. First,as noted in Chapter 1, the nautical chart isprepared for several types of users. Althoughrecreational vessels may draw 6 feet or less,


Continued on next page

TABLE 4-3Selection Criteria For Charted Soundings

Least Depths:Least depth soundings over features (e.g., pinnacles, domes, ridges), which are delineated by depthcurves should be identified because they are typically associated with hazardous shoal areas. Whenapplying hydrography from larger to progressively smaller scales, a series of shoals may have to begeneralized into a single-shoal feature. In this case, the most shallow sounding is selected to representthe least depth over the generalized shoal. The least depth of a natural channel (also termed the control-ling depth) is also charted. Every natural channel has at least one controlling sounding, which identifiesthe minimum depth of the channel.

Critical Soundings:Within each isolated feature bound by a depth curve, the shallowest seaward sounding must be se-lected. By definition this is a critical sounding and is given even if the same as the depth curve. Criticalsoundings represent least depths in proximity to known or potential navigational routes. Note that while acritical sounding is almost always a least depth, a least depth is not always a critical sounding; thelocation of the sounding is also an important factor.

Deep Soundings:Deeps, like shoals, are local deformations of the bottom shape. Soundings which are approximately 10%to 20% deeper than their surroundings are considered important soundings and will usually be selectedby cartographers. If chart space is constrained, however, a deep sounding does not normally takeprecedence over an adjacent critical shoal sounding.

Supportive Soundings:Supportive soundings (also termed developmental soundings) supply additional information to the userabout the shape of the bottom. These are also used to provide periodic identifiers for depth curves andto show changes in bottom slope away from shoals or deeps.

Fill Soundings:Fill soundings are used to portray smooth bottoms or deep areas between shoals that are not ad-equately defined by supportive soundings. Normally, fill soundings provide information about large,gradually sloping depressions that are not deep enough to be enclosed by a depth curve. Ideally fillsoundings radiate away from the deep sounding.

Channel Range Soundings:When a range is charted to show the centerline of a channel, a line of soundings is selected on therange. This policy does not apply to improved (dredged) channels.

Nonjunction Soundings:When the application of a recent survey to a chart reveals conditions so changed that a satisfactoryjunction cannot be made with the hydrography of former surveys, a blank band of approximately 5mmshall be left beyond the limits of the more recent survey and a note added, such as: “Hydrography to(eastward) from surveys of 1984.”

Changeable Areas:All hydrographic detail, including soundings and floating aids, may be omitted from all areas known toundergo continual and rapid change, such as ocean inlets and openings between barrier islands. (Seefigure 5-7 in chapter 5.)


�Charting PracticesSoundings information is shown on the

chart by many small printed figures, each de-noting a particular sounding. Soundings in tra-ditional units (fathoms, feet) are shown in con-ventional (vertical) type, soundings in metricunits (meters and tenths) are charted in italictype.2 Soundings are charted in their exactgeographic location, and oriented parallel tothe base of the chart, even if the chart projec-tion is skewed.

All hydrographic detail and floatingATONs are removed from certain areas un-dergoing continual and rapid change, such asocean inlets and openings between barrier is-lands if inclusion of this information mightpresent an unreasonable risk to mariners. Thearea of omitted soundings is tinted in blue, andan explanatory note charted, as shown in fig-ure 5�7 in the following chapter. Normally,only small-draft vessels would consider usingsuch areas, but some of these areas are fre-quented by larger draft commercial vessels�

sometimes with unpleasant consequences (seeWalsh, Professional Mariner, Issue No. 5). Thesafest course of action is to imagine theseareas have �Keep Out� signs posted. On small-scale nautical charts, soundings within agroup of rocks or coral heads through whichthere is no well-defined channel are also omit-ted .

Depth Curves (Section I of Chart No. 1)In addition to sounding data, depth infor-

mation on nautical charts is summarized bycharted depth curves and labels. According tothe Desk Reference Manual, a depth curve�

�...is a line connecting points of equalwater depth which is sometimes sig-nificantly displaced outside of sound-ings, symbols, and other chart detail forclarity as well as safety. Depth curves,therefore, often represent an approxi-mate location of the line of equal depth[a depth contour] as related to the

Table 4-3—ContinuedSelection Criteria For Charted Soundings

Soundings in Slips and Around Piers:Soundings in docks, slips, and around piers should be shown where space allows. The cartographershould select soundings far enough off piers to provide depths at the keel lines of vessels which usethese piers.

Depths over Rocks:A sounding over an isolated rock shall have the label “Rk” placed next to it.

No Bottom Soundings:When no bottom is reported in the survey, the measured depth shall be shown under a bar with a smalldot over it. (This type of fill sounding shall be avoided whenever possible.)

River Depths:The shoreline shall be broken to accommodate soundings for narrow rivers where the sounding unitswould touch the shoreline because of the size of the feature at chart size. When portraying hydrographyin navigable tributaries, the cartographer must select soundings that indicate controlling depths inconjunction with those that portray the best navigational channel. Where feature size or chart scale donot allow for the representation of both controlling depths and channel depths, the controlling depthstake precedence.

SOURCE: Adapted (with minor word changes) from Nautical Chart Manual.

2The difference in type face serves to alert mariners to the difference in depth units.


surveyed line delineated on the source.The term curve is often used collec-tively for both depth curves and depthcontours.� [Material in brackets addedfor clarity]

Depth curves complement the sounding dataand enable the mariner to form a better men-tal image of the shape of the ocean bottom.Griffin and Lock, writing in the CartographicJournal, offer the following comments on con-tours,

�The origins of the contour may remainindistinct, but in its earliest known(submarine) form it manifested twomajor advances from the earlier spo-radic use of spot heights (soundings).Firstly, it provided spatial continuityof information, developing a statisticalsurface from a set of discrete controlpoint data, thereby introducing addi-tional information by the process of in-terpolation. Secondly, it simplified thesymbol array and stressed the need forvisual integration of the contours toform a mental image of the configura-tion of the surface of the lithosphere.�

Depth curves (or contours) resemble elevationcurves used to depict topographic relief (seeChapter 3), but there are subtle conceptual dif-ferences between these terms. Kember, alsowriting in The Cartographic Journal, offersthese colorful insights on the use and inter-pretation of depth contours on Admiralty nau-tical charts; comments equally applicable toNOAA charts,

�Depth contours also receive treatmentthat may surprise topographic cartog-raphers. For years, in hydrographic de-partments all over the world, thesewere hardly regarded as contours at allbut as danger lines meaning precisely�keep out.� Each depth contour said�keep out� to a particular type of ves-sel. The 1-fathom line warned smallriver and fishing vessels; 2 fathoms�many coasters, colliers, small ocean-

going ships; 3 fathoms�the majority ofocean-going ships. For the mighty few,the largest battleships and the proud-est ocean liners, the 5-fathom line wasspecially provided. As �keep out� linesthey were drawn to embrace all depthsthat might possibly offer danger to avessel of the appropriate type. Caughtin the contour�s net were often a largenumber of depths greater in value thanthe contour itself, but nobody mindedthe ninety and nine greater depthscaught inside so long as there was notone lesser depth left in outer darkness.

�Today marine cartographers aremore inclined to treat contours in themanner of our topographic colleaguesand to allow contours to play their partin revealing underwater topography.But when it comes to the crunch�andwe must simplify or generalize�we do,deliberately and knowingly, and on be-half of the navigator, include all lesserdepths within a contour even if it meansthat our catch includes many deep onesas well.

�So on the Admiralty Chart the de-piction of depth is a curious mixture ofthe exact (high accuracy of spot sound-ings for example) coupled with thisdanger fixation which gives greatprominence to lesser depths. The re-sult is a navigator�s bathymetry�a verydifferent thing from a bathymetrist�sbathymetry. In spite of appearances thechart is not a navigational document ofthe superimposition type. It has some-thing of the underground map�s ruth-less selectivity and single minded userorientation.�

Depth curves are used on charts to illustrateshallow areas, shoals and banks, irregular bot-toms, navigable channels and passages, anddeeps�much the same information as thatidentified in table 4�2 for soundings.

Depth curves are particularly relevant tonavigators using electronic depth sounders. Of


course, the mariner must make adjustmentsfor the placement of the echo sounder withrespect to the surface of the water and for thestate of the tide in order to compare the ob-served depth with the charted depth. For ex-ample, assume that the observed reading onthe echo sounder is 15 feet of water under thekeel, the position of the transducer is 3 feetbeneath the vessel�s water line, and that thecalculated height of tide is 7 feet (relative tochart datum). To reduce these data to a figurecomparable to the charted depth, it is first nec-essary to add the difference between the loca-tion of the transducer and sea level, and thensubtract the calculated height of tide, so thecomparable figure would be 15 + 3 - 7 = 11 ft.

Guidelines for charting depth curves ab-stracted from the Nautical Chart Manual in-clude:

The development of curves varies ac-cording to the particular bottom fea-ture being charted. Large shal lowareas are generally represented by asparsity of depth curves, while banksand bars and isolated shoals are repre-sented by a series of closely spaced con-tour closures.In areas with irregular bottoms, con-tours are selected for each isolatedshoal�s least depth. Supportive sound-ings and curves are then selected to re-inforce this least depth as well as to de-fine the zones between the shoals. Thishelps to convey to the user the largedepth variations in the area.

Smooth bottom areas are characterizedby smoothly flowing and relativelywidely spaced contours with only oc-casional closures identifying shoals.

Depth contours are particularly usefulin showing natural channels from deepwater into shore or harbor areas androutes between deep-water areas

through shoals. If the chart scale is toosmall to illustrate all the channelsshown on the survey, the most impor-tant routes are retained in preferenceto less important routes.

Depth curves are not typically shownaround charted isolated deeps in shal-low areas, unless the deep is part of anatural channel. Depth curves will usu-ally be shown with charted deeps indeeper water. Isolated deep curves arealways supported with a sounding in-s ide.

Depth curves around depressions areof little value, and are not typicallycharted. However, these are shown ifthey reveal features which may havesome navigational value, or if they in-dicate the deepest side of a river.

Very steep slopes would entail numer-ous closely spaced depth curves and cre-ate a problem in terms of chart clutter.In this case the shallowest and thedeepest curves are retained in lieu ofless important intermediate curves.

A series of standardized values fordepth curves is employed. For example,the standardized curve intervals whendepth is given in feet includes (in feet),6,3 12, 18, 24, 36, 60, 120, 180, 240, 300,etc. For metric charts the standard in-tervals (in meters) are, 2, 5, 10, 20, 30,40, 50, 60, 70, 80, 90, 100, 200, 300, etc.

�Charting PracticesOn earlier charts, depth curves were de-

picted using a variety of symbols (see SectionI 30 in Chart No. 1), line weights, and colors.This section details present charting practices.Charting conventions for the depiction ofdepth curves include lines or curves, labels,and a blue tint.

3In addition to the �standard� curves, a 3-foot curve is also used in some shallow water areas, such as theFlorida keys.


�SymbolDepth curves are charted with a solid black

(blue on some charts) line of 0.10 mm thickness.Approximate depth curves are charted with adashed line. These curves may be broken for curvelabels (the depth) and chart notes. However,curves do not overprint any other charted fea-ture. Depth curves are charted to scale as de-picted on source documents, but may be general-ized. (Where generalization is necessary, a curveis always displaced toward deeper water, unlessthis closes or seriously reduces the width of anavigable channel. The minimum width betweendepth curves identifying a natural channel is 0.3mm.)

�LabelsDepth contour/curve labels are shown in italic

type for charts where depths are given in feet/fathoms. Labels for depth contours and curveson metric charts with italic soundings are printedin conventional type. The convention of printingsoundings and curve labels in different type (e.g.,vertical if soundings printed in italic) preventsany confusion between the estimated contour leveland actual soundings. The contour or curve lineis broken for the labels with the label centeredon the line. As a general rule, labels are placedalong the lines at 10 cm to 15 cm intervals so asnot to interfere with soundings and other charteddata. In congested areas, labels may be staggeredalong the lines if this improves the legibility ofthe chart. All depth contours and curves arelabeled in the same unit as the soundings shownon the chart (e.g., in meters for metric charts, infeet if soundings are given in feet, etc.).

�Shallow Water Tint(s)A blue tint (Blue Tint No. 1) is shown on the

chart to emphasize shallow water areas consid-ered dangerous to navigation. The depth contourselected as the boundary for the tinted area is nota constant for all charts, but rather determined bythe chart scale, prevailing depths available, andthe draft of the vessels expected to navigate withinthe charted area. The limit value for the tint forany chart can be determined by noting the sound-ings on either side of the tinted area (see Kals).

Having said this, the limit of the blue-tinted areais typically the 6-foot curve on harbor charts, andthe 12-, 18-, or 30-foot curves on coastal charts(Dutton, Chapman).

For some charts two separate tints are used,Blue Tint No. 1 and a lighter Blue Tint No. 2. Theuse of two tints enables two depth zones to bedelineated; the second depth zone (deeper andtinted in a lighter blue) expands the usefulnessof the blue-tinted danger area to another groupof chart users.

Figure 4�4 provides an excerpt from NOSChart No. 13218 (Martha�s Vineyard to Block Is-land) which illustrates many of the chart conven-tions discussed above. In this case, the limit ofthe blue tinted area is the 30-foot curve. Depthcurves are shown at 30, 60, 90, 120, and 150 feet.Note that the soundings density is greatest inshoal areas and where necessary to characterizethe shape of the depth curves.

�Improved (Artificial) ChannelsUnlike natural channels, improved (artificial)

channels are those which are dredged to estab-lish and maintain project depths. The side limitsof improved channels are shown on charts bydashed lines (I 22 of Chart No. 1). Depth curvesare not shown for improved channels. Channeldepth information is either tabulated or shownwithin or adjacent to the channel.

Controlling depths are charted in feet on non-metric charts (including those with soundings infathoms) and meters and decimeters on metriccharts.

Channels for which graphic surveys are re-ceived by NOAA and which are 400 feet or morein width (Type 1) for their major portion pro-vide depth information tabulated by quarters;channels 100 feet to 400 feet (Type 2) are tabu-lated by outside quarters and middle half; andchannels less than 100 feet (Type 3) are tabu-lated by full width. On charts where dredgedchannel legends and tabulations are adequatelycovered by larger scale charts, the legend andtabulation are omitted, a �(see note)� placed inthe channel, and a note (preferably on a landarea of the chart) is added, as illustrated by thefollowing example:


Fig. 4-4. Excerpt from NOSChart No. 13218 (Martha's

Vineyard to Block Island). The30-foot curve is the limit of

the blue tint. Depth curves areshown at 30, 60, 90, 120, and

150 feet. Note that the sound-ings density is greatest in

shoal areas or where neces-sary to characterize the shapeof the bottom. The character-istic of the bottom is princi-

pally rocky, and there arenumerous sunken rocks inthe area. Two dangerous

sunken wrecks can be seen,with unknown depths.


BEAUFORT INLET

The project depth is 30 feet toMorehead City. For controlling

depths, use chart 11547.

If the reported depth is less than the charteddepth, an additional notation such as �Re-ported shoaling in channel 1986� is added.

�SymbolsDashed lines are used to show channel lim-

its for improved channels. The line thickness,length of dash, and space vary with the type ofchannel. Blue tint is charted inside the limitsof improved channels when the project depth orcontrolling depth is equal to or less than thevalue of the charted blue tint curve or when theseaward end of an improved channel terminatesin a blue tint area, regardless of channel depth.

Figure 4�5 presents an excerpt from NOSChart No. 12314 (Delaware River, Philadelphiato Trenton), which shows how improved chan-nels are depicted on the nautical chart. A tableof channel depths is included elsewhere on thischart. Controlling depths in this area are be-tween 16 and 18 feet according to surveys of 1-91. There is actually a powerplant located nearthe two stacks to the right of the Duck IslandRange. Barges laden with coal are unloaded atthe overhead conveyor. Note that barges com-ing from seaward (the south) cannot travel di-rectly to the conveyor from the main channel.Rather, they must be pushed north to thePerriwig Channel to avoid shoals and rocks.Here is indisputable evidence of the benefitsof a chart!

Bottom CharacteristicsThe character of the bottom is identified on

all nautical charts, particularly in harbors, des-ignated anchorages, and all other areas wherevessels may anchor. Bottom characteristics de-termine the suitability of the area for anchor-ing, and the type of anchor best suited to thearea (see Hinz, or the introduction to appen-dix A).

Bottom characteristics are of interest forother reasons. According to the Nautical ChartManual, bottom characteristics are charted to

provide the following information;

�1. They assist fishermen in selectingareas where fish may be found andin avoiding places where nets andequipment may be damaged.

�2. In tidal areas, they show where ves-sels may safely take the ground atlow water.

�3. In shoal areas, they help navigatorsto assess the stability of shoals andto dist inguish rocky areas fromareas of unconsolidated materials.�

Descriptors used for bottom characteristicsare shown in Section J of Chart No. 1. The mostcommonly used bottom characteristics on nau-tical charts are provided in table 4�4. Defini-tions of these terms are given in appendix A.Nouns and their abbreviations begin with acapital letter; adjectives or qualifying wordsand their abbreviations are composed of lower-case letters only. Bottom characteristics arecharted in black italic type.

Figure 4�4 also shows the use of bottomdescriptors. In the area around Block Island,the bottom is described in various places as�hrd� (hard), �rky� (rocky), �Blds� (boulders),�yl S Sh G� (yellow sand, shells, and gravel),and �M S G� (mud, sand, and gravel).

Specific Hazards to NavigationThe balance of this chapter addresses spe-

cific hazards to navigation, including dangercurves, rocks, shoals, ledges and reefs, foul ar-eas, wrecks, obstructions, marine structures,unexploded ordnance, and dangerous water con-ditions. Many of these objects/areas have spe-cial symbols described in Chart No. 1. Specificreferences to section of Chart No. 1 are shownin parentheses. Thus, for example, the symbolused to represent the danger curve or dangerline is shown in Section K, item 1, of Chart No.1. It is noted in what follows as �danger curve(K 1).� Although pertinent excerpts of Chart No.1 are included in this and other chapters, spaceconstraints do not permit inclusion of the en-tire chart in this manual. Users should read this


Fig. 4-5. Excerpt from NOS Chart No. 12314 (Delaware River, Philadelphia to Trenton). This excerptillustrates the chart conventions for depicting improved channels. A table of controlling depths for

each channel segment is shown elsewhere on the chart.

manual with a copy of Chart No. 1 at hand forready reference.

As a point of general interest, it is useful tonote the type convention used to depict theseobjects/features. Vertical type is used for namesof topographic features and fixed objects, whichextend above high water�i.e., �bare� featuresare shown in conventional type. Slant (italic)type is used for names of hydrographic features,including names of water areas, underwater fea-tures, and floating ATONs (see Chapter 5). Be-

cause this convention is common to all charteditems discussed below, a discussion on typestyles is not repeated in each of the subsections,except where necessary for clarity.

The various specific dangers to navigationare charted principally to alert the mariner tosubmerged artificial and natural hazards. How-ever, it should be noted that certain types ofvessels may congregate in these areas, andpresent an additional collision hazard. Thus,for example, private and charter fishing vessels


ChartAbbreviation

SourceAbbreviationNoun

ChartAbbreviation

SourceAbbreviationAdjective

Adjectives

ColorsColor AbbreviationBlackBlueBrownGrayGreen

OrangeRedWhiteVioletYellow

blbubrgygn

orrdwhviyl

Nouns

TABLE 4-4 Bottom Characteristics and Abbreviations

BrokenCoarseDarkFineGritty

HardLargeLightRockySmall

SoftSpeckledSticky

brkcrsdkfnegty

hrdlrgltrkysml

sftspkstk

bkcdkfgty

hlrgltrkysml

sospksy

BouldersClayCoralCoral headGravel

GrassMudOozePebblesSand

ShellsShingleSiltStonesSeaweed

BldsClCoCl HdG

GrsMOzPS

ShSnSiltS tWd

BldsCyCoCl HdG

GrsMOzPS

ShSnS iStWd

SOURCE: Nautical Chart Manual


may be found in the vicinity of fish havens andwrecks, dive boats may be found in the area ofcharted wrecks, and service vessels of varioustypes may be found in the area of artificial plat-forms. Rule 5 of the Navigation Rules specifies:

�Every vessel shall at all times main-tain a proper look-out by sight andhearing as well as by all availablemeans appropriate in the prevailingcircumstances and conditions so as tomake a full appraisal of the situationand of the risk of collision.�

Particular vigilance is appropriate in areas ofgreatest vessel density.

Figure 4�6 provides an excerpt of SectionK from Chart No. 1, which illustrates many ofthe symbols referenced in what follows.

Danger Curve (K 1)According to the Desk Reference Guide, a

danger curve�

�...is a dotted curve used to draw thenavigator�s attention to a danger whichwould not stand out clearly enough ifit were represented on the chart solelyby other specific symbols. This dottedcurve is also used to delimit areas con-taining numerous dangers, throughwhich it is useful to navigate.�

Danger curves are used to outline areas or em-phasize discrete features (e.g., rocks, shoals,submerged structures) that are known or po-tential hazards to navigation. As with depthcurves generally, the limiting line is alwayscharted on the side of safety�that is, the dan-ger curve is either drawn to scale or slightlylarger, to help ensure that any errors are con-servative.

Submerged structures covered by 66 feet, or11 fathoms (20 meters) or less are indicated by adotted danger curve enclosing the symbol for theparticular danger. If the structure is covered bydepths greater than 11 fathoms (20 meters), thedanger curve is charted only if the structure isconsidered hazardous to navigation.

�Charting PracticesThe danger curve is charted with a black

dotted line. Insofar as possible, the danger curveis charted in its exact geographic position. Thiscurve is an integral part of other symbols usedto depict hazards. If chart space presents a prob-lem for inclusion of a specific symbol within adanger curve, the symbol may be omitted andonly the depth included. Areas enclosed by adanger curve that are less than 2.5 mm in diam-eter at chart scale are charted with the mini-mum size circle 2.5 mm in diameter. Adjacentfeatures individually enclosed with a dangercurve may be enclosed with a common general-ized curve on small-scale charts. A blue tint isused within a danger curve to mark depths of 66feet or 11 fathoms or less. The blue tint can beused in areas of greater depths if the object is con-sidered a hazard to navigation.

�Labels and NotesAppropriate labels are included to describe

the danger being enclosed with the dangercurve.

Rocks (K 10-17, a, b, f)According to the Desk Reference Guide, a

rock�

�...is an isolated large mass of stone, usu-ally one constituting a danger to navi-gation. Rock is a collective term formasses of hard material generally notsmaller than 256 mm.

Rocks are classified as bare, awash,rocks awash at the sounding datum only,or sunken. Bare rocks are those extend-ing above the plane of mean high water[MHW see figure 4�1]; rocks awash arethose exposed at some stage of thetide; �sunken rocks are those coveredat the chart datum. A sunken rock is po-tentially the most dangerous naturalhazard to navigation. When selectingrocks for [charting], the character of thearea, whether exposed or protected; theproximity to shore; the range of tide; andthe probable visibility of the rock at somestage of the tide are factors to be con-sidered. Special care shall be used in


Fig. 4-6. Excerpt from Section K of Chart No. 1Continued on next page

General

Danger line, in general : .. ...

2 .ll,Obstr (3;:: (.~.~. '.' .. ".} 0.5. .l1Rk t....:.:..:::.: _ Swept by wire drag or diver

Rocks

Plane of Reference for Heights --4H Plane of Reference for Depths ~H

~Il\\''''' ®3.1) 6(1·7) " I,;:

<® Rock (islet) which does not cover, ~ II~~ 10 #

(21) • height above height datum (4m)

~ *Uncov 2ft • 69(27) * (J)) * (J6)

CD Rock which covers and uncovers, ~ijlr--

/ 11 *(2) \I(Zl Q.Jncov 2 ft \?:: .;t:. height above chart datum

*(2) \I(Z)

~ ;+; :))j;. ) if. , .. ~ (iD

12 ;+; :)¥:;. Rock awash at the level of chart ® ~ \I(Q) datum I"",

~~\--

) + ,+,) '.f .' .... 13 + ~±: Dangerous underwater rock of

uncertain depth

'" '-I'- -...J\~ 14 Dangerous underwater rock of ( +(48))

'I\) / ! ) / +(121~CC

known depth

14.1 12 Rk in the corresponding depth area ~

"----- -/\....

/ \)/ /

/ 't." (48 ) /" / '),.\) * (12,)

14.2 ::~::Rk outside the corresponding depth area ~

7~ 1\



15 + 35Rk Non-dangerous rock, depth known

16 ..... + ... .+ ...

·{f.(!ft.f Lin.~.·· _/.~ ...• ............ ( '\ Coral reef whiCh covers

Breakers

Wrecks

Plane of Reference for Depths ~ H

20 C=:> C=>Hk C=>Hk Wreck, hull always dry, on large-scale charts

21 C=:>Hk Wreck, covers and uncovers, on large-scale charts

22 Submerged wreck, depth known, on large-scale charts

23 Submerged wreck, depth unknown, ::==:'>Hk

on large-scale charts

24 ~ ~PA Wreck showing any portion of hull or superstructure at level of chart datum

25 ·:fP: Masts .... ~·-:.:/Mast (10 Ft) Wreck showing mast or masts !· ..... Funnel above chart datum only

26 ::~:Wk Wreck, least depth known by sounding only

27 .£LWk ±,wk .£l. Wk JL (~} Wk WreCK, least depth known, swept by wire drag or diver Wk

28 +B Dangerous wreck, depth unknown

29 +++ Sunken wreck, not dangerous to surface navigation

- Wreck, least depth unknown, but

30 «Wk considered to have a safe clearance to the depth shown

21 R

. + -i: ... /'"+Co + Co· ":.. + + ........ ~ .... + .'

d /

/'7 /

/ / r..,,/Wk

...... / ·52"· ·Wk

.... : .. ..........

<".· ... /Wk

~

'+':·Mast

{i.~>Wk

::1~)Wk

.:+.:.

+f+-

-(25:Wk

19 @Sr

18

... {?,.5,)Wk

(25}Wk ~

C> c:::::::> Wk Wk

C: . ."::::::> ~ Wk Wk

C[> Wk

C=:> C=:> Wk Wk ........

::B-t:. > c=> Wk

C· :::/. c=> Wk Wk

:+-B (9)

+++ .£LRk

(l§)



31

(f.."9Xjl:.: (W.F.~}

#

Obstructions

(f.9:~l:::

(W.F.~}

(W.C~£~~~2~.\

Plane of Reference for Depths ~ H

40

41

42

43.1

43.2

44.1

44.2

45

C: Obstn

@::Obstn

(~)Obstn ±Obstn

o 1. Sub m piles

Stakes, Perches

00 Snags

I 1111 111111 1111

: ~ ......... .! \ ..... , .\

..•...... Obstruction l ...... ...: (fish haven)

46.1 l~~ (actual \ ••••••. i shape)

Obstn

{~t: Obstn

J .•••••

{ c£i. ": Obstn ........... :"5·: Obstn 2..:.:..

00 Subm piles

Subm piling

00 Stumps

Fsh stks

: ....... Obstruction ~ ... j (fish haven) ,-----, I I L

46 2 - - ..., Fish haven }

Obstn

. I I (Authmin 42ft) I __ J

47 /---..

< ..... Oys ) ---

Remains of a wreck or other foul area,

dangerous to navigation should

be avoided by vElssels anchoring,

trawling etc.

Obstruction, depth unknown

Obstruction, least depth known

Obstruction, least depth known,

swept by wire drag or diver

Stumps of posts or piles, a/l or

part of the time submerged

Submerged pile, stake, snag, well

or stump (with exact position)

Fishing stakes

Fish trap, fish weirs, tunny nets

Fish trap area, tunny nets area

Fish haven (artificial fishing reef)

Fish haven with minimum depth

Shellfish cultivation (stakes visible)

r-----,

I F 0 u I I L ____ J

Kelp, Sea-Weed ~J

£Obstn

...... Obstn

1

r-----' I Fish traps I L _____ J

i Obstn

r'\ r

r-----l I Tunny nets I L _____ J

L~ .......

: .. ~ ... ........ 2

4 ........... .

r (f) Subm piles


ContinuedFig. 4-6. Excerpt from Section K of Chart No. 1

Supplementary National Symbols

a * .¥ Rock awash (height unknown)

b (~:: Rk (~.~:s Shoal sounding on isolated ::~# ,it-rock or rocks / 2' ....

0(8) ..... p..)

C Sunken wreck covered 20 to

:+±+: 30 meters

d (jSub vol Submarine volcano

e ("' '-....JOiscol water Oisco/ored water

~i: ..... Sunken danger with depth Obst.n

f .£LRk (~) cleared (swept) by wire drag .£1 C ...... :: ~

9 Reef Reef of unknown extent

h 0 :~ko €iD 0 Coral reef, detached (uncovers

QCo :*:Co at sounding datum)

-i r __ J Sub m Submerged Crib 0

Crib

j 0 Crib Crib (above water) (above water)

k Submerged Crib with depth 0(2')

I Crib w ith d rYing height 0 (2)


charting dangerous rocks. Isolated anddangerous rocks, whether bare, awash,or sunken, shall be emphasized by a dan-ger curve encircling the symbol.� [Mate-rial in brackets has been inserted for clar-ity.]

Rocks are particular hazards to navigation.Running into a rock not only grounds the ves-sel�problem enough�but also may severelydamage the hull of the vessel. Attempts to freethe vessel may only make matters worse if thehull was damaged by the grounding (Cahill,Minnoch).

Bare rocks, however, can serve as usefullandmarks for fixing a vessel�s position. A suffi-ciently prominent bare rock at or near a sunkenrock or other danger may be an excellent natu-ral marker for the sunken hazard�a naturalwreck marker. In cases where the bare rock isin the general vicinity of invisible hazards tonavigation, this rock can be used by the marinerto establish a danger bearing or danger circle(see Bowditch, Dutton).

�Charting PracticesCharting conventions consist of a symbol, and

various labels or notes, which could include theheight of the rock, depth of water over the rock,and the name of the rock. Names and labels orrocks covered or periodically covered at certaintide levels or that refer to the sounding datumare charted in black italic type. Correspondinglabels for bare rocks are shown in vertical type.Symbols and labels are discussed below.

�Rocks Symbols and LabelsThe classification of rocks shown on NOAA

charts varies according to the geographic loca-tion of the charted area�Atlantic and gulfcoasts, Pacific coast, and Great Lakes. For thisreason, separate remarks are included for eachregion.

�Bare Rock (K 10)A bare rock (islet) is defined as one with an

elevation at least 2 feet above MHW for the At-lantic and gulf coasts, at least 3 feet above MHWfor the Pacific coast, and at least 5 feet or moreabove low-water datum for charts of the Great

Lakes. An islet is charted in its exact geo-graphic location. Islets are drawn to scale (ifpossible at the chart scale). If not, the bare rocksymbol (K 10) is used. On small-scale charts,the minimum size (0.5 mm by 0.65 mm) symbolmay exaggerate the size of the rock. If known,the elevation (in feet or meters above the chartdatum) is shown in vertical type enclosed inparentheses.

In some cases, fixed ATONs are located on arock. The light or daybeacon symbol (see Chap-ter 5) takes precedence over the rock symbol.(Cartographers take particular care to restorethe rock symbol if the light or daybeacon ismoved.)

�Rocks Which Cover and Uncover (K 11)A rock which covers and uncovers (rock

awash) is defined as a rock with an elevation 1foot above MLLW to less than 1 foot above MHWfor the Atlantic and gulf coasts, 2 feet aboveMLLW to less than 2 feet above MHW for the Pa-cific coast, and 2 feet above low-water datum to 4feet above low-water datum for the Great Lakes.A rock awash is charted in its exact geographiclocation and shown to scale if possible. If not,the symbol (K 11) for this type of rock is used. Ifknown, the elevation (in feet or meters abovethe chart datum) is given in vertical type. Forthese rocks, the elevation is charted in verticaltype enclosed in parentheses and underlined.

�Rocks Awash at the Level of Chart Datum(K 12)

A rock awash at the level of chart datum isdefined as a rock with an elevation 1 foot belowMLLW to less than 1 foot above MLLW for theAtlantic and gulf coasts, 2 feet above MLLW toless than 2 feet above MLLW for the Pacific coast,and 2 feet below low-water datum to less than 2feet above low-water datum for the Great Lakes.This rock is charted in its exact geographic lo-cation and shown to scale if possible. If not, thesymbol (K 12) for this type of rock is used.

�Sunken Rocks (K 2, 13)A sunken or submerged rock is defined as a

rock covered more than 1 foot at MLLW for theAtlantic and gulf coasts, more than 2 feet atMLLW for the Pacific coast, and covered more


than 2 feet at low-water datum for the GreatLakes. If the depth is unknown, a special sym-bol (K 13) is charted. If the depth is known, it isgiven (in feet or meters relative to chart datum).

A depth determined by a wire-drag surveyis denoted by a special symbol (K 2). The maxi-mum wire-drag cleared depth over a rock ischarted.

Critical dangers to navigation, includingrocks, located under bridges are charted intheir position on the largest scale chart cover-age. The bridge symbol is broken when suchdangers are charted beneath the bridge struc-ture�a policy that reflects the potential im-portance of the hazard.

Figure 4�7 provides illustrations of chartconventions for numerous hazards to naviga-tion.

�Doubtful Danger LabelsIn some cases information regarding rocks

or other specific hazards is uncertain or incom-plete. A series of labels (and associated defini-tions) has been developed and may be appendedto the symbol. According to the Desk ReferenceGuide, these labels include:

�SD� (Sounding Doubtful). Of uncer-tain depth. This shall be used whena depth shown on a chart over a rockis strongly suspected of being lessthan that stated. The position is notin doubt.

�Rep� (Reported). The �Rep� labelshall be attached to a charted rockbecause it is considered dangerousto navigation, but which has not beenconfirmed by an authoritative fieldobservation party. The year the fea-ture is reported shall be included aspart of the label (e.g., Rep (1985)) andshall be enclosed with parentheses.�Rep� may be combined with theother labels in these groups.

�ED� (Existence Doubtful). Of uncer-tain existence. The expression shallbe charted to indicate the possible ex-istence of a rock, the actual existenceof which has not been established.

�PA� (Position Approximate). Of in-exact position. The expression shallbe charted to state that the positionof a rock has not been accurately de-termined. The plotting of an objectfrom preliminary data is not of thedesired accuracy [10 feet, see Chap-ter 6] . . ., but it is acceptable for in-terim charting until an accurate po-sition is available.

�PD� (Position Doubtful). Of uncer-tain position. This expression shallbe charted to indicate that a sub-merged rock has been reported invarious positions but no one positionhas been definitely verified. The ex-istence of the feature is not in ques-tion, only its correct position.

Similar labels are used to depict other hazards,so these labels are not repeated in each of thefollowing sections. As a practical matter, mari-ners would do well to resolve the cartographers'uncertainty by assuming that the feature ex-ists. Where adequate safe water exists adjacentto the feature, mariners should simply avoidthe potentially hazardous area.

Shoals (K b, O 25)According to the Desk Reference Guide, a

shoal�

�is an offshore hazard to navigation onwhich there is a depth of 16 fathoms (30meters) or less, and is composed of anymaterial except rock or coral.�

Although not all shoals are hazards to naviga-tion for all vessels�note that shoals can havecharted depths as great as 30 meters�shoalscertainly represent a hazard for deep-draft ves-sels. Moreover, water over a shoal may be dis-turbed and present other hazards to recre-ational vessels even if there is sufficient depthover the shoal. Finally, the prudent marinershould remember that shoals can shift loca-tion�particularly after storms or in areas ofstrong currents. Where these conditions areknown, these are noted as �changeable areas�and hydrography is not reported. However,care is always required when navigating shoalareas (e.g., Professional Mariner, Issue No. 1).


Fig. 4-7. Excerpt from NOS Chart No. 12366 (Long Island Sound and East River). Thisexcerpt shows a number of hazards, including danger curves, foul areas, sunken

rocks, wrecks, obstructions, and pipeline and cable areas.

33 36

..... sA 43 "" 32 - - - ~~ _____ _

7

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as 40

Cable Area

43

57 85

82 70

75

64

74

54

56

66

71 92

81

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61

67

56

93

92 83

81

100

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/ /

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.< V 1'9 /~ C, S3 •

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75

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�Charting PracticesShoals are depicted by soundings, danger

curves, and blue tint as appropriate (see above).Shoals are charted in their exact geographicpositions. Shoals carry the primary label�Shoal� (or abbreviation �Shl� where space islimited) in black italic type. The label may in-clude the name of the shoal (e.g., �NebraskaShoal�). If the danger is doubtful or its posi-tion approximate, the appropriate qualifiers(i.e., �SD,� �PD,� �ED,� or �PA�) are included.

Ledges and Reefs (Various)According to the Desk Reference Guide,

ledges and reefs are defined as follows:

�A ledge is a rock formation connectingand fringing the shore of an island orlarge land mass; it is generally charac-terized by a steep sheer in the subma-rine topography.

�A reef is a rocky or coral formation dan-gerous to surface navigation which mayor may not uncover at the sounding da-tum. A rocky reef is always detachedfrom shore; a coral reef may or may notbe connected with the shore.�

Reefs and ledges are further subdivided intouncovering ledges and reefs (J 21, J 22, K h),submerged ledges and reefs (K 16, K g), and oys-ter reefs (K 1, K 47). Obviously, reefs and ledgesrepresent a major hazard to navigation. Run-ning aground on ledges and reefs, as with rocks,entails the ever present danger of structuraldamage. Moreover, these are (at least at somepart of the tidal cycle) invisible dangers to navi-gation. Their depiction on the nautical chartis, therefore, particularly important.

�Charting PracticesCharting conventions consist of a symbol and

various explanatory labels and notes.For uncovering ledges and reefs standard

symbols (J 21, J 22, and K h) are charted. A la-bel is added when scale permits to identify thefeature, e.g., �Rock� or �Coral.� Names may beincorporated into the label.

Submerged ledges and reefs are shown by

a danger curve (black dotted line), and blue tintto delineate the limits of the feature. A label isadded to further identify submerged ledges andreefs, e.g., �Subm ledge� or Subm reef.� Depthsover rocks and coral heads within submergedledge or reef limits are charted using sound-ings and labels, e.g., �5 Rk� or �5 Co Hd.� If thedepth over these features is unknown, the sub-merged rock symbol (K 13) is used with theappropriate label.

On small-scale charts where space con-straints limit the amount of detail that can beincluded, the most shallow depth over the sub-merged ledge or reef is included in the label.As with other underwater features, labels areshown in italic type, e.g., �Subm ledge (cov 5feet at MLLW).�

Oyster reefs are charted using the samecharting conventions. If oyster reefs bare at thechart sounding datum, green tint is added tothe dotted danger curve. A label is added toidentify oyster reefs, e.g., �Oyster Bar,� or �Oys-ter Reef� in italic type. Oyster reefs and barsare charted if these present a hazard to navi-gation or upon request or recommendation ofstate or local agencies for informational pur-poses.

Foul Area (K 31)According to the Desk Reference Guide, a

foul area�

�is an area of numerous uncharted dan-gers to navigation. The area chartedserves as a warning to the mariner thatall dangers are not charted individuallyand that navigation through the areamay be hazardous.�

A foul area is an area where the bottom isknown to be strewn with rocks, reefs, boulders,coral, obstructions, heavy concentrations ofkelp, or other debris that could impede navi-gation. Foul grounds should be avoided by ves-sels intending to anchor or engage in activities,such as trawling, which could be adversely af-fected by the presence of hazards in the foularea (e.g., nets could snag). The term foul doesnot apply to areas where the bottom is soft (e.g.,mud or sand) or composed of other bottom


materials not likely to cause damage to a ves-sel or otherwise restrict activities.

�Charting PracticesA foul area is charted with a limiting dan-

ger curve (see above) and label(s). A blue tintand soundings data may also be included.

�Symbol (K 31)The symbol for a foul area (K 31) may be

shown in isolation, but may also be combinedwith other symbols, e.g., those for rocks, to pro-vide a more complete description to the mari-ner.

Important visible objects located in foul ar-eas, which are useful as landmarks (see Chap-ter 6 for chart conventions for landmarks), arealso charted. These landmarks can alert themariner to the presence of the foul area and beused for danger bearings, etc. (see Bowditch,Dutton).

Foul areas are charted in their exact geo-graphic positions as provided in the source ma-terial available to cartographers. Where pos-sible, foul areas are charted to scale to showthe actual size and shape of the actual foul area.Foul areas less than 2.5 mm in diameter atchart scale are charted with the minimum size(2.5 mm) symbol. A blue tint is added to foulareas dangerous to navigation, generally thosehaving depths of 66 feet or 11 fathoms (20meters) or less, when enclosed with a dangercurve and not supported by depth contours andsoundings.

�Label(s) and NotesDescriptive labels, including �Foul,� �Foul

Area,� �Boulders,� �Blds,� �Kelp,� �Danger line,��Reef line,� are included to indicate the type ofdanger present. Labels are printed in blackitalic type.

Wrecks and Hulks (K 20-31)According to the Desk Reference Guide,

�A WRECK is the ruined remains of avessel which has been rendered useless,usually by violent action, such as theaction of the sea and weather. In hydrog-raphy the term is limited to a wrecked

vessel, either submerged or visible,which is attached to or foul of the bot-tom or cast upon the shore.

�A HULK is generally defined as theremnants of an abandoned wrecked/stranded vessel, the actual shape ofwhich is shown on large-scale charts.May also be used to define stored or per-manently berthed vessels where actualshape is shown on large-scale charts.�

Wrecks depicted on nautical charts are clas-sified as either stranded or sunken (NauticalChart Manual). A stranded (visible) wreck isdefined as one which has any portion of the hullor superstructure above the sounding datum.Submerged wrecks are located below the sound-ing datum or have only the masts visible.

Wrecks are continually subject to the effectsof current and weather. As a result, wrecks canchange in physical form and in location. Par-ticularly if not visible and at depths at or nearthe draft of the vessel, wrecks present a haz-ard to navigation. Important information re-ceived on �new� wrecks or changes in the sta-tus of existing wrecks are published in the NMand LNM.

Wreck locations are not only of interest tomariners seeking to avoid potential dangers,but also to divers and charter captains. Fish-ing vessels using nets generally avoid areaswith wrecks because of the potential for wrecksto snag or damage nets.

�Charting PracticesAll stranded and sunken wrecks are charted

on the largest scale chart nautical chart of thearea. Wrecks not classified as dangerous (seebelow) are omitted on charts smaller than1:150,000 scale in areas covered by larger scalecharts. Charting conventions for wrecks/hulksconsist of a symbol, labels and notes, and blueor yel low t int . Addit ional ly , doubt ful orquestionable wrecks are so noted by appropri-ate label (e.g., �PA,� �PD,� �ED,� etc).

�Symbols, Labels, and TintsStranded wrecks are charted with a stan-

dard black symbol (K 24) which may face either


left or right. The baseline of the symbol isshown parallel to the bottom of the chart, andthe small �circle� at the base of the symbol (lookclosely at the symbol) marks the publishedposition of the wreck. If the scale of the chartis sufficiently large, the true outline of astranded wreck is shown with a solid line, land(gold) tint, and labeled. If a significant portionof the wreck is determined to be bare at theSPOR, it is considered a topographic featureand labeled with vertical, rather than italic,type.

Sunken wrecks are considered dangerousto navigation if any part of the wreck lies at 66feet or 11 fathoms (20 meters) or less below thesounding datum. Wrecks deeper than 66 feetor 11 fathoms may also be considered danger-ous in areas expected to be traveled by deeperdraft vessels. Wrecks in areas where waterdepths and submerged features have been re-moved (changeable areas) are not charted asthis information could be misleading. Danger-ous sunken wrecks are denoted by one of sev-eral symbols (K 25-28) as noted below:

Dangerous wrecks lacking precisedepth information and those wherethe depth over the wreck is unknownare charted with the center crosslines of the dangerous wreck sym-bol (K 28) marking the published po-sition of the wreck. The symbol is ro-tated so that it is coincident with theknown alignment of the wreck. If thealignment of the wreck is unknown,the symbol is aligned with thebaseline of the chart. A blue tint isadded for emphasis within the en-closing danger curve.

Sunken wrecks with only theirmasts visible at the sounding datumare charted using symbol (K 25)with the added label �Masts.�

A dangerous wreck over which aprecise least depth has been deter-mined is charted with a soundingsurrounded by a dotted dangercurve, blue tint, and a label (K 26).

A cleared depth obtained by a wire-drag survey over a dangerous wreckis shown with a sounding sur-rounded by a dotted danger curve,blue tint, a wire-drag symbol out-side the danger curve below thesounding, and the label �Wk� (K 27).

The label �Wreckage� and a dotteddanger curve (K 31) is used to iden-tify areas where numerous danger-ous wrecks are located or where thewreckage is scattered. Blue tint isadded within the danger curve.

Sunken wrecks that are not deemedto be dangerous to surface vesselsexpected to frequent the area arecharted with a sunken wreck sym-bol only (K 29).

�Wrecks Marked by BuoysBuoys used to mark dangerous wrecks are

charted in their exact position if possible (seeChapter 5). However, if the chart scale doesnot permit showing both symbols in their ex-act locations, the wreck is charted in its exactlocation, and the buoy is moved slightly.

Obstructions (K 40-42)According to the Desk Reference Guide, an

obstruction�

�is anything that might hinder marinenavigation. An obstruction on a nauti-cal chart is usually considered to be ahard, unyielding isolated object, such asa sunken rock or manmade article com-monly located in deeper depths, thatwould endanger or prevent the safe pas-sage of vessels. The term �obstruction�is often used as a preliminary label forreported dangers until they can be iden-tified and properly labeled, and includessuch objects as submerged piles, sunkenwrecks, uncharted rocks, etc.�

From the mariner�s perspective, obstructionshave the same significance as rocks or wrecks�obstructions are objects that may present a


hazard to navigation. The majority of itemscharted as obstructions are reported to NOAAthrough the NM and LNM and from USCGAUXand USPS reports.

�Charting PracticesThe guidelines for classifying an obstruc-

tion as dangerous to surface navigation are thesame as those used for sunken wrecks androcks�e.g., those covered by 66 feet or 11 fath-oms (20 meters) or less of water, unless in anarea frequented by deeper draft vessels. Anunidentified submerged object that is not con-sidered to be the remains of a submergedwreck and is not considered a danger to sur-face navigation is termed a �Snag� rather thanan obstruction.

Obstructions are charted with symbols, la-bels, and a blue tint. Appropriate qualifiers(e.g., �ED,�), discussed above, are included ifthe obstruction is questionable or uncertain.

�Symbols and LabelsThree symbols are used to depict obstruc-

tions (K 40-42), depending upon the availabledepth information. These objects are chartedto scale in the exact position of the obstruc-tion and enclosed with a danger curve filledwith blue tint. If the chart scale does not per-mit a rendition to scale, the minimum size(2.5 mm) circle is used. All obstructions carrythe label abbreviation �Obstn� in black italictype.

Snags are charted with a 1 mm circle andlabeled �Snag.�

The depth over the obstruction is chartedif known. In cases where a cleared depth overthe charted position has been obtained from awire-drag survey, the label �cleared __ ft 19__�is added.

Natural Dangers (K 43.2)Natural dangers include deadheads, logs,

snags, and stumps. Running into any of thesedangers can cause structural problems and/ordamage propellers. (It is generally agreed bymost mariners that propellers are not thedepth sounding apparatus of choice!) Defini-tions and charting practices for these naturaldangers are described briefly below.

A deadhead is a grounded log or treetrunk often floating free at one endor below the surface of the water. Adeadhead is usually charted with a1 mm circle and labeled �Snag.�

Logs that are grounded with someparts visible above the surface of thewater are charted in some cases.These logs are charted with a 1 mmcircle and labeled �Snag.�

A tree or branch embedded in ariver or lake bottom and not visibleon the surface is charted as a snag.

Stumps are the stationary remainsof trees, often submerged. Theseare labeled �Stumps.�

Fish Havens Regulated by State andFederal Permits (K 46.1, K 46.2)

Fish havens are artificial shelters con-structed of rocks, concrete, car bodies, andother debris and put on the seafloor to attractfish. Fish havens are often found in the vicin-ity of fishing ports or major coastal inlets andare usually considered hazards to navigation(and certainly to anchoring). Some fish havensare periodically altered, which increases thepotential hazard.

�Charting PracticesFish havens are denoted with a symbol

(K 46.1, K 46.2), labels/notes, soundings, andblue tint (if considered a danger to naviga-tion). Fish havens are charted in their ex-act position and to scale�subject to a mini-mum dimension of 2 mm to ensure that thechart feature is readily recognizable. Fishhavens with authorized minimum depths of66 feet or 11 fathoms (20 meters) or less arecharted with a dotted limiting danger curveand blue tint. Those greater than 66 feet or11 fathoms are charted with a dashed lim-iting danger curve and no tint, unless thefish haven is considered to be a danger tonavigation, in which case the blue tint isused. The label �Fish Haven� is appended.

Fish havens are often marked with privately


maintained buoys. These are charted if pub-lished in the LNM but omitted otherwise.

Miscellaneous HazardsOther hazards that are charted when con-

sidered dangerous to navigation include ma-rine structures (e.g., platforms and cribs, fish-ing and hunting structures, drilling platforms),fishing structures (e.g., fish/crab pens, fishstakes, and fish traps, weirs, tunny nets), float-ing structures (e.g., floats, floating breakwaters,and floating piers), logging structures (logbooms), mineral development structures (e.g.,wells, wellheads, platforms, and artificial is-lands). Charting practices are similar to thoseidentified above. Space constraints do not per-mit an exhaustive discussion of each of thesehazards in this manual. A brief sampling of thechart symbols used to depict these hazards in-cludes:

Platforms and Cribs; charted astopographic features if at or abovethe shoreline plane of reference,charted as hydrographic features ifbelow the shoreline plane of reference.

Fish Stakes (K 44.1)

Fish Traps, Weirs, Tunny Nets (K44.2, K 45)

Floating Breakwaters (F 4.1)

Log Booms (N 61)

Wells (L 20)

Wellheads (L 21.1-21.3, L 13)

Artificial Islands (L 15)

Dolphins (F 20), Piles (F 22, K 43.1,K 43.2)

Unexploded OrdnanceAccording to the Desk Reference Guide, the

term unexploded ordnance�

�...refers to any undetonated explosive

material which is reported to be outsidethe charted limits of established regu-lated explosives dumping areas.(Unexploded bombs, depth charges, tor-pedoes, ammunition, pyrotechnics, etc.)�

Unexploded ordnance generally does not posea hazard for transiting vessels, but anchoringin these areas could be risky. Other activities,such as diving, or use of fishing nets would alsobe imprudent. (Disentangling a torpedo ordepth charge from a fouled net would presentan unwelcome challenge!) Unexploded ord-nance is charted when reported in LNM or byreliable sources. Sunken wrecks containingunexploded ordnance are considered danger-ous wrecks and so charted.

�Charting PracticesCharting conventions for unexploded ord-

nance consist of a symbol and explanatory la-bels.

�SymbolsUnexploded ordnance areas are outlined

with a dashed line. The ordnance is charted inits exact geographic positions. The dashed limitlines are charted to scale. If the area is lessthan 2.5 mm in diameter at chart scale, the mini-mum size 2.5 mm symbol is used. The size ofthe unexploded ordnance area includes an al-lowance for the uncertainty of the reported po-sition.

Sunken wrecks containing unexploded ord-nance are charted with the dangerous sunkenwreck symbol (see above).

�Labels and NotesUnexploded ordnance areas are labeled (in

black italic type) �Unexploded Ordnance,� fol-lowed by the year the hazard was reported,�(Reported 19__),� in parentheses beneath thearea label. Sunken wrecks carrying unexplodedordnance are labeled �Wk (Unexploded Ord-nance).� The type of ordnance (e.g., bombs,depth charges, etc.) may be charted if known.

Unsurveyed Area (I 25)According to the Desk Reference Guide, an

unsurveyed area�


�...is an area on a nautical chart wherehydrographic surveys are unavailable orlimited. These areas are usually labeled�Unsurveyed.� �

Unsurveyed areas are charted to alert themariner to areas where depth information isunknown. In general, hydrographic detail is notcharted in areas of continual and rapid change.If a recent survey reveals conditions so differ-ent that a satisfactory match (junction) cannotbe made with the hydrography of former sur-veys, a blank band is charted beyond the limitsof the more recent survey.

�Charting PracticesUnsurveyed area limit lines are charted

with a dashed line (I 25). A blank space approxi-mately 5.0 mm wide is charted between the lim-its of hydrographic surveys that fail to matchsatisfactorily.

The label �Unsurveyed Area� is charted inblack italic type. In constantly changing areas,an appropriate note explaining the lack of hy-drography is charted in black. Where surveysdo not junction satisfactorily, a note (e.g., �Hy-drography to (eastward) from surveys of 1934�)is charted in black italic type.

Dangerous Water Conditions (Various)According to the Desk Reference Guide, dan-

gerous water conditions�

�...are physical characteristics of waterincluding visible movement, coloring,and the presence of marine vegetationthat constitute a hazard to navigationor indicate the presence of submergedobstructions or shoal areas.�

Illustrative dangerous water conditions in-clude rapids/waterfalls (C 22), breakers (C d,K 17), overfalls/tide rips/races (H 44), eddies(H 45), kelp (J 13.2), discolored water (K e), andcurrents (H 40, 41, H m, t). Their relevance tosafe navigation is so obvious as not to requirefurther explanation.

�Charting PracticesExtensive dangerous water conditions are

outlined and labeled to identify the condition.Small areas are charted with symbols or labelsonly. On conventional and small-craft nauticalcharts or areas where significant tidal currentsexist, tidal current arrows (H 40, 41, H m, t)are charted at locations selected from the �Cur-rent Differences� listed in the latest edition ofthe Tidal Current Tables.

�SymbolsAs noted, limits to dangerous water areas

are charted in their exact geographic positionswith a dashed line or (for small areas) with vari-ous symbols.

�Labels and NotesA label describing the nature of the condi-

tions is charted to provide further information.Labels are charted with capital and lower caseletters in black italic type; e.g., �Tide Rips.� Dis-colored water�often an indication of shoals�is abbreviated �Discol Water,� or �Discol� ifspace is at a premium.

Where particularly strong currents exist, alabel and a note may be charted in addition toa current arrow and velocity label. The follow-ing note provides an illustrative example;

�CURRENTS AT SERGIUS NARROWS

At times the velocity reaches 8knots. On an average, the current turnsfrom North to South about 2 hours be-fore the time of high water at Sitka andfrom South to North about 1-3/4 hoursbefore the time of low water at Sitka.

For more precise information con-sult the Pacific Coast Current Tables ofthe National Ocean Service which in-cludes predictions of the times of slackand times and velocities of strength forevery day of the year.�

Additional information on currents may beprovided in the form of a current diagram (H t)or limits to major currents, such as the GulfStream.


Although not necessarily considered a dan-gerous water condition, tidal information is rel-evant to the mariner, and presented in sum-mary form on the nautical chart. Informationon the height of the water is presented in twoforms, tide notes for areas with appreciabletidal range, and hydrographs (diagrams show-ing seasonal variability in water levels) forcharts of the Great Lakes. In either case, thesedata are averages of water levels only, and notspecific predictions. The notes alert the mari-ner to the presence of large variations in wa-ter level, and the need to consult other refer-ences for tidal predictions.

Submarine Pipelines and Cables(L 30.1�44)

Submarine pipelines and cables can be dam-aged as a result of vessel groundings. Anchorscan also damage these objects, and anchoringrestrictions are in effect in these areas. More-over, submarine pipelines may present signifi-cant hazards to navigation, similar to a sub-merged wreck, rock, or other hazards discussedabove.

Submarine cables include those used forpower transmission and those used for commu-nications. Damage to either can have signifi-cant adverse consequences (e.g., loss of power,disruption of communications) as well as caus-ing damage to the vessel and/or its propellers.

�Submarine Pipelines (L 40.1, 40.2, 41.1,41.2, 43, 44)

Submarine pipelines are partitioned intofour classes; those used for nonvolatile mate-rial transport, potable water intakes, volatilematerial transport, and abandoned (or unused)pipelines.

Nonvolatile material transport pipe-lines are conduits for the intake ofnonpotable water (e.g., for cooling orirrigation purposes) and for dis-charge of wastes (e.g., cooling water).

Potable water intakes are structuresdesigned for the intake of drinkingwater. These are usually elevated

above the bottom and supported andprotected by a debris-screeningstructure (a crib), which is sepa-rately charted. These are charted inthe Great Lakes and other freshwa-ter inland lakes.

Volatile material transport pipe-lines are used to convey liquids andgases, usually petroleum or othermineral products of a hazardous na-ture. Collisions with, or dragging ananchor on, these pipelines also en-tail the risk of pollution incidents,explosions, and fires.

Abandoned (unused) pipelines areno longer in service, but still presenta hazard to navigation.

Chart symbols and conventions differamong these pipeline classes. All pipelines maybe charted either as an individual pipeline, orincluded in a pipeline area.

�Individual PipelinesIndividual pipelines are charted using sev-

eral symbols, labels, and notes.

Intake and discharge pipes (nonvola-tile material transport) are chartedin black using a unique symbol (L41.1). This symbol is directional�theball part of the symbol being placedat the end furthest from the assumedsource of flow. No label is added.Conduits for discharging effluents;e.g., industrial, chemical, sanitary,and storm water discharge, arecharted with the same black symbol(L 41.1) and labeled �Sewer� in italictype on the largest scale chart andon smaller scales as space permits.

Potable water intakes are chartedusing one of two black symbols (L41.1, L 43), and labeled �PWI� initalic type.


Abandoned pipelines are charted inblack using a unique symbol (L 44)without any label.

Pipelines used for liquids and gas-ses are depicted by a unique magentasymbol (L 40.1) without any label.

In addition, the following caution note (inmagenta vertical type) is added to all chartscontaining submarine oil and gas pipelines andsubmarine cable areas:

�CAUTIONSUBMARINE PIPELINES AND CABLES

Charted submarine pipelines and sub-marine cables and submarine pipelineand cable areas are shown as:

Symbols (L 40.2, L 30.2)

Additional uncharted submarine pipe-lines and submarine cables may existwithin the area of this chart. Not all sub-marine pipelines and submarine cablesare required to be buried, and those thatwere originally buried may have becomeexposed. Mariners should use extremecaution when operating vessels indepths of water comparable to theirdraft in areas where pipelines andcables may exist, and when anchoring,dragging, or trawling.

Covered wells may be marked bylighted or unlighted buoys.�

�Pipeline AreasAs noted above, pipelines can be charted

individually or in areas. Pipeline areas areshown in magenta by dashed area limits (L 41.2)and labeled �Pipeline Area.� According to theNautical Chart Manual:

�The extent of the limits of the area willbe governed by local conditions (e.g., thenumber of pipelines or cables) but shallin all cases include the immediate areawhich overlies the pipeline or cables.

The limiting lines shall be spaced 1,000feet apart or 500 feet on each side of thepipeline or cable position or from theouter ones of a group, or a minimum of5.0 mm at charting scale for small-scalecharts. Cable and pipeline areas shallbe labeled in Newton Light Italic type,capital and lowercase letters, with typesize appropriate to the size of the fea-ture or scale of the chart.�

�Submarine Cables (L 30.1, 30.2, L 31.1, L32)

According to the Nautical Chart Manual:

�Cables are classified as power cablesand communication cables. Power cablesare used to transmit electricity across alarge expanse of water where overheadtransmission is not feasible, or in areasof heavy commercial shipping wheregreater danger would exist by use ofoverhead transmission. Communicationcables are used to transmit messages.Submarine cables shall be chartedwithin protected waters such as harbors,rivers, bays, estuaries, or other inlandnavigable waterways to warn the mari-ner of possible interference with navi-gation and to help prevent damage tocables from anchors. Cable and pipelineareas should not be charted in large ar-eas void of hydrography, except to showthe terminus of a line.�

As with pipelines, cables can be charted in-dividually or in areas.

�Individual CablesPower cables are depicted by one of two

magenta symbols (L 30.1 �generic cable,� or L31.1). Abandoned or unused cables are depictedby a unique magenta symbol (L 32). Communi-cations cables are depicted by a magenta sym-bol (L 30.1). The continuity of the wavy-line sym-bol (L 30.1) is not broken for soundings or otherchart details except where legibility of theoverprinted feature would be impaired. No la-bels are included.


�Cable AreasCable areas are charted in the same man-

ner as pipeline areas, except that a unique sym-bol is used (L 30.2).

Other Relevant Sources of InformationIn addition to the nautical chart and Chart

No. 1, several other sources provide informa-tion on hydrography and specific hazards tonavigation. These include the U.S. Coast Pilot,Local Notices to Mariners, and the Tide Tablesand Tidal Current Tables.

U.S. Coast PilotThe U.S. Coast Pilot contains valuable ma-

terial on hydrography and hazards to naviga-tion that supplements the nautical chart. Inparticular (see the Coast Pilot Manual), thispublication provides textual information onaquacultural sites, bars, basins, channels, cur-rents, dangers depths, fish havens, fishtraps,heights, submarine features, tides, and wrecks.In general, the U. S. Coast Pilot provides nar-rative material that goes beyond that providedby the symbols, notes, and legends used on thenautical chart. For example, the guidance of-fered in the Coast Pilot Manual for a descrip-tion of bars, dangers, submarine features, andwrecks is:

�Bars. Where a bar is dangerous, stateunder what conditions it is danger-ous and describe the most favorableconditions for crossing. Statewhether the bar breaks in ordinaryweather or only in heavy weatherand how far out the breakers extend.Give the least depth at the best placefor crossing the bar (where there isno dredged channel)�.

�Dangers. Give kind and extent of natu-ral dangers; least depths over them;if they break, at what stage of thetide; and how much, if any, is bare atthe chart datum. Do not list each in-dividual danger in a group; a descrip-tion of the most prominent, or the onenearest the channel, or the one far-thest from shore is usually sufficient.

�Submarine features. Describe the char-acter of the bottom slope, especiallywhen approaching the shore. Statewhether soundings can be dependedupon to warn of the approach to dan-ger. Note any special submarine fea-tures, such as valleys and escarp-ments, that may be useful in depthcurve navigation.

�Wrecks. Describe dangerous wrecks inor near channels not maintained(dredged) by the Corps of Engineersand along established routes or likelypassage. . . . Do not discuss wreckslying well offshore unless theypresent a hazard in a normal coastalroute or in the approach to port (e.g.,within a safety fairway). A wreck ly-ing amid other described dangersshould not be mentioned, nor shouldthose lying in shallows or other ar-eas out of the way of normal naviga-tion.�

The U.S. Coast Pilot reads as though an ex-perienced mariner, with local knowledge, werebriefing the navigator. For example, here arethree brief excerpts from the U.S. Coast Pilot,Volume 3, Atlantic Coast: Sandy Hook to CapeHenry (1993) applicable to waters off Cape May,N J .

�The approaches to Delaware Bay havefew off-lying dangers. The 100-fathomcurve is 50 to 75 miles off Delaware Bay,and the 20-fathom curve is about 25 milesoff. Depths inside the 20-fathom curveare irregular, and in thick weather adeep-draft vessel should not approachthe coast closer than depths of 12 fath-oms until sure of its position; the safestapproach or passing courses would beoutside Five Fathom Lighted Buoy F andDelaware Lighted Horn Buoy D.

�The shoals off Cape May are mixed clayand sand and have the consistency of


hardpan; the ridges run in approximatelythe same directions as the currents. CapeMay Channel, 1-mile southwest of thecape, is an unmarked passage betweenshoals, with depths from 2 to 6 feet oneither side. The channel is seldom used,and then only by fishing vessels and plea-sure craft; local knowledge is requiredfor safe passage.

�The channels have strong currents, andmany tide rips form near Prissy WicksShoal, which has depths as little as 2 feetabout 2 miles south of Cape May Light.In Cape May Channel, the current ve-locity is 1.5 knots on the flood and 2.3knots on the ebb.�

Tide Tables and Tidal Current TablesThese publications, described in Chapter 1,

provide information necessary to estimate theset and drift of the current, and the height ofthe tide at any time for numerous locations. Tideand current information provided on the nau-tical chart is very general, and use of the TideTables and Tidal Current Tables is recom-mended.

Notice to Mariners (NM)The NM is a bulletin in pamphlet form is-

sued weekly by the National Imagery and Map-ping Agency (NIMA). NM contains all correc-tions, additions, and deletions to all NIMA andNOAA charts.

Local Notice to Mariners (LNM)The USCG Local Notice to Mariners (LNM)

contains important information on changes tohydrographic features and dangers to naviga-tion. Charts should be corrected with the LNMbefore being used.

With respect to hydrographic features, theLNM provides information on changes to chartsfor individual features; e.g., a revised depthover a charted hazard, and more general infor-mation. In some cases, the revised informationcan be described fully by a simple narrativestatement; e.g., �Add, dangerous wreck at lo-cation.� In other cases, a chartlet is provided

in the LNM showing the updated information.The chartlet is published in the exact scale ofthe chart being updated, so that all that is nec-essary is to cut out the chartlet and paste itover the corresponding area of the nauticalchart. Figures 4�8 and 4�9, for example, pro-vide an illustration from NOS Chart No. 12366and the revised chartlet published on Decem-ber 6, 1993. This chartlet was included to amendthe published soundings and depth curve datain the East River, near the Throgs Neck Bridge,NY. As can be seen in this example, the changesare substantial, and chart correction is particu-larly easy.

Concluding RemarksNo attempt is made to summarize this ex-

tensive chapter. Rather, it is fitting to concludewith some general remarks on chart accuracyand tips for using the hydrographic informa-tion provided on charts. Some of the sugges-tions are identical to those furnished in otherchapters. These points are also made here foremphasis.

The Admiralty Manual of Navigation offersthe following comments on the reliability ofnautical charts:

�� no chart is infallible; every chart isliable to be incomplete in some way oranother. Charts based on lead-line sur-veys are particularly fallible; a singlelead-line sounding, which surveyed atbest a few centimeters on the sea bed,may be reflected by a figure occupyingseveral hectares of ground depending onthe scale of the chart. Any such chartbeing used for pilotage would have tobe treated with the greatest suspicion.

� The degree of reliance to be placed ona chart must depend upon the charac-ter and completeness of the original sur-vey material and on the completenessof reports and subsequent changes.Apart from any suspicious inconsisten-cies �matters which must be taken intoaccount are the scale of the chart, itssoundings in relation to the dates of thesurveys or authorities from which it has


Fig. 4-8. Excerpt from NOS Chart No. 12366(Long Island Sound and East River). The areashown was subject to a correction in the LNM.

~ ~ '0

<{? ....

% v v ~

~ '0

~ ~~

~ ~

~ % ~

~ ~

~ ~

~~ ~

~ % %

~ ~ ~

v v ... ~

V

~


Fig. 4-9. Chartlet LNM issued to correct exhibitshown in Figure 4-8.


been compiled and examination of thechart itself. Even these considerationscan only suggest the degree of relianceto be placed on the chart. The chartmust never be taken for granted.�

Although NOAA produces some of the fin-est nautical charts in the world, even thesecharts have some limitations. Depth informa-tion on nautical charts is based on soundingsfrom the latest available hydrographic surveywhich, in many cases, may be quite old. Theage of hydrographic surveys supporting nau-tical charts varies. Approximately 60 percentof inshore hydrography was acquired byleadline (pre-1940) sounding technology. Themariner should consult the source diagram toidentify areas recently surveyed. Where pos-sible, courses should be selected that pass throughrecently surveyed areas.

Always use the largest scale chart of thearea to be navigated.4 Large-scale charts pro-vide the greatest amount of hydrographic de-tail for a small area as well as showing moreATONs and landmarks. Ensure also that thechart has been corrected with information pro-vided in the NM and LNM. These points areespecially important if using electronic charts.It is very tempting to �zoom out� on the chartscale in an attempt to �fit in� the entire trackin setting waypoints. However, this may ob-scure important information on hazards tonavigation. Remember also that most elec-tronic charts are obsolete shortly after pro-duction. There is no presently available sub-

stitute for a corrected large-scale paper chart,although this may change in the future.

Remember that the general appearance ofthe sea bottom is likely to resemble the adja-cent land features, even if the chart soundingsdo not show this pattern. For example, if theadjacent land mass has steep hills, is strewnwith boulders and rocks, and rocky islands arefound offshore, the sea bottom is likely to havea similar appearance. Look carefully at thecharted depths and bottom contours. Adjacentdepths that differ greatly from one another(shown on the chart or observed on the depthfinder) indicate boulders, pinnacles, or othernatural hazards that project upwards from thesea bottom. These areas are most likely tohave uncharted natural hazards. Leave an ex-tra margin�an ample safety margin�of depthunder the keel in such areas. Also, where pos-sible, travel in well-established channels inpreference to other areas.

Safety margins are important in the hori-zontal, as well as the vertical plane. Unless thevessel�s mission is to voyage to a charted haz-ard, any hazard should be given a wide berth.(In figuring a horizontal safety margin, it isimportant to consider the probable error inthe vessel�s position�i.e., different marginsare appropriate depending upon the naviga-tion systems in use.)

Be particularly careful when voyaging inareas, such as changeable areas, for which hy-drographic information is not charted. Natu-ral channels in certain inlets or other areaswhere there are strong currents change fre-

4Amazingly, operators of even commercial craft�such as the skipper of the tug Mauvilla (which raninto a railroad bridge precipitating an AMTRAK rail wreck in September 1993)�sometimes venture forthwithout charts, let alone corrected large-scale charts (see Anon, Professional Mariner, 1994).

In another incident (Anon, Professional Mariner, Issue No. 1) the Little Gull, an offshore clamboatskippered by a hired delivery captain, ran aground off Brigantine, NJ. The vessel was found to have nofixed compass and no charts of the area of the grounding. The captain was quoted as saying that he neverplots anything on a chart and rarely refers to them. �I don�t have to plot; I just know it all by heart. My brainis so impregnated with loran bearings (sic) that I can figure out where to go without charts.�


quently, and should be used only by marinerswith local knowledge.

Fix the vessel�s position at frequent inter-vals. This reduces the likelihood of strayingfrom the intended track into more hazardousareas. If the vessel�s position is appreciablyoff course, plot a revised track to ensure thatit is safe to return to the original course.

The U.S. Coast Pilot and other sources,such as commercial cruising guides, should beconsulted for additional information. Othermariners with local knowledge are also use-ful sources. (However, do not blindly follow

other vessels in the belief that they knowwhere they are going, unless their draft is con-siderably greater than yours!)

Finally, mariners should make it a pointto report chart discrepancies/update. In or-der-of-magnitude terms, there are approxi-mately 2,000 employees involved in one aspector another of chart production�including hy-drographic survey crews�but nearly 16 mil-lion recreational boats owned. Even if only asmall fraction of these boaters were to sendchart updates to NOAA, the quality of nauti-cal charts would improve significantly.

� � � � � � � � � � � � � � � � � � � � � � � � � � � �

�The sound navigator never trusts entirely to the ob-vious. The price of good navigation is constant vigilance.The unusual is always to be guarded against and whenthe expected has not eventualized, a doubtful situationalways arises which must be guarded against by everyprecaution known to navigators� It is always the cap-tain who is sure in his own mind, without the tangibleevidence of safety in his possession, who loses his ship.�

Excerpt from Report of Court Inquiry investigating thePoint Honda disaster in 1923.

� � � � � � � � � � � � � � � � � � � � � � � � � � � �


References

Anon. �Fishing Vessel Hits Beach in Naviga-tional Blunder,� Professional Mariner, Is-sue No. 1, 1993, p. 29.

��. �Keeping a Low Profile,� Profes-sional Mariner, Issue No. 5, 1994, p. 29

. ��. �Shifting Shoals Snag Slag Ship,�Professional Mariner, Issue No. 1, 1993, p.30.

Brogdon, W., �The Limits of Charting,� OceanNavigator, Issue No. 57, November/Decem-ber 1993, pp. 75, et seq.

Bunyon, D., �The United Kingdom Hydro-graphic Office,� The Cartographic Journal,Vol. 28, No. 1, June 1991.

Cahill, R. A., Disasters at Sea, Titanic to ExxonValdez, American Merchant Marine Foun-dation, Kings Point, NY, and NauticalBooks, San Antonio, TX, 1991.

��. Strandings and Their Causes,Fairplay Publications, London, UK, 1985.

Cohen, P.M., Bathymetric Navigation andCharting , United States Naval InstitutePress, Annapolis, MD, 1970.

Defense Mapping Agency, Hydrographic/To-pographic Center. American PracticalNavigator, An Epitome of Navigation(Bowditch), Publication No. 9, NIMA StockNo. NV PUB 9 V1, Bethesda, MD, 1995.

Ekblom, R., �Role of Hydrography in MarineInvestigation and Litigation,� Lighthouse,Journal of the Canadian Hydrographic As-sociation, Edition No. 44, Fall 1991.

Griffin, T. L. C., and B. F. Lock. �The Percep-tual Problem in Contour Interpretation,�The Cartographic Journal, Vol. 16, No. 2,December 1979.

Hinz, E. The Complete Book of Anchoring andMooring, Cornell Maritime Press,Centreville, MD, 1986.

Human Technology, Inc. Desk ReferenceGuide: Specifications Unit, Chart and Map,Feature: Channel. Report developed forNational Ocean Service, Charting and Geo-detic Services, Marine Chart Branch, Un-der Contract OPM-85-77, McLean, VA,October 1985.

��: Danger Curve.��: Dangerous Curve.��: Dangerous Water Conditions.��: Depth Curve.��: Feature.��: Fish Haven.��: Foul Area.��: Ledge and Reef.��: Low Water Line.��: Natural Resources.��: Obstruction.��: Platform.��: Rock.��: Ruins.��: Shallow.��: Shoal.��: Tides.��: Unexplained Ordnance.��: Unexploded Ordnance.��: Unsurveyed Area.��: Wire Drag and Swept Area.��: Wreck.

Kals, W. S., Practical Navigation, Doubleday& Company, Gordon City, NY, 1972.

Kember, I. D., �Some Distinctive Features ofMarine Cartography,� The CartographicJournal, Vol. 8, No. 1, June 1971.

Lockwood, C. A. and H. C. Adamson., Tragedyat Honda, Chilton Company�Book Divi-sion, Philadelphia, PA, 1960.

MacPhee, S. B., �How Often Should Charts BeReissued?,� Lighthouse, Journal of the Ca-nadian Hydrographic Association, EditionNo. 30, November 1984.

Magee, G. A., �The Admiralty Chart: Trendsin Content and Design,� The CartographicJournal, Vol. 5, No. 1, June 1968.


Maloney, E. S., Chapman Piloting, 60th Edi-tion, Hearst Marine Books, New York, NY,1991.��. Dutton�s Navigation and Piloting,Fourteenth Edition, Naval Institute Press,Annapolis, MD, 1985.

Minnoch, J. E., Aground! Coping with Emer-gency Groundings, John de Graff, Inc.,Clinton Corners, NY, 1985.

Ministry of Defence, Directorate of Naval War-fare. BR 45(1) Admiralty Manual of Navi-gation, Vol. 1, Her Majesty�s Stationary Of-fice, London, UK, 1987.

Pielou, F. A., �Special Purpose NavigationCharts,� The Cartographic Journal, Vol. 8,No. 1, June 1971.

Richards, Capt. T.W., �Modernizing NOAA'sMarine Navigation Services,� Sea Technol-ogy, June 1994.

Sabellico, Lt. M.S., �QE II Grounding,� OnScene, COMDTPUB 16100.4, 3/92.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration, Na-tional Ocean Service, and Department ofDefense, National Imagery and MappingAgency. Chart No. 1 United States ofAmerica Nautical Chart Symbols Abbre-viations and Terms, Ninth Edition, Wash-ington, DC, January 1990.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration, Na-tional Ocean Service. Coast Pilot Manual,5th Edition, Rockville, MD, 1994.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration, Na-tional Ocean Survey, HydrographicManual, Fourth Edition, Rockville, MD,July 4, 1976.

U.S. Department of Commerce, Coast and Geo-detic Survey, Nautical Chart Manual, Vol-ume One: Policies and Procedures, SeventhEdition, Washington, DC, 1992.

U.S. Department of Transportation, UnitedStates Coast Guard. Navigation Rules, In-ternational�Inland, Commandant Instruc-tion, M 16672.2B, 17 August 1990.

Walsh, G., �Chartroom Chatter,� Ocean Navi-gator, Issue No. 50, November/December1992, p. 18.

Walsh, G., �Treacherous Inlet Snags AnotherShip,� Professional Mariner, Issue No. 5,February 1994, pp. 24, et seq.

Zoraster, S., �The Automatic Selection of PrimeSoundings for Nautical Chart Compila-tion,� Lighthouse, Journal of the CanadianHydrographic Association, Edition No. 41,Fall 1991.

.

Aids to Navigation 5-1

Introduction and OverviewAccording to accepted NOAA Nautical

Chart Manual nomenclature, an Aid to Navi-gation (ATON)�

�...is a man-made structure/device exter-nal to a craft designed to assist in de-termining the craft�s position or a safecourse or to warn of dangers or obstruc-tions. When the information is transmit-ted by light waves, the device is a visualaid to navigation; if by sound waves, anaudible aid to navigation; if by radiowaves, a radio aid to navigation. Any aidto navigation using electronic equip-ment, whether or not radio waves areinvolved, may be considered an elec-tronic aid to navigation. The term �aidto navigation� should not be confusedwith the more general term �naviga-tional aid� which covers any instrument,device, chart, method, etc., intended toassist in the navigation of a craft.�

A more complete list of ATONs and associatedinformation normally found on nautical chartsis provided later in this chapter. Briefly, how-ever, ATONs include such objects as buoys,lights, fog signals, daybeacons, range markers,radiobeacons and LORAN-C and Omega lat-tices. Although the GPS certainly satisfies the

definition of an ATON, this system is not dis-cussed in this chapter, because GPS informa-tion is not provided on nautical charts. Omegais also not discussed in this manual eventhough Omega information is provided on cer-tain nautical charts because small craft are notgenerally equipped with these receivers. Fi-nally, charted LORAN-C information is not in-cluded in this manual because this is coveredat length in the USCG LORAN-C User Hand-book, to which the reader is referred.

ATONs may be fixed (land-based or fixedstructures in the water) or floating (e.g.,buoys). Landmarks are the functional equiva-lent of ATONs but, because these have notbeen especially constructed for this purpose,are not formally classified as ATONs. Land-marks are treated in a separate chapter(Chapter 6. Landmarks) of this manual.

This chapter provides information on thetype and utility of ATONs and how these aredepicted on nautical charts. (Because ATONsare so important to safe navigation and, there-fore, charted in great detail, this chapter is longand detailed.) The chapter also identifies thesources of additional information (e.g., theChart No. 1, U.S. Coast Pilot and the Light List)which supplement that provided on the nauti-cal chart. As appropriate, practical commentsare made throughout the chapter on the correctuse of ATONs for marine navigation. (See also

CHAPTER 5

Aids to Navigation

� � � � � � � � � � � � � � � � � � � � � �

�An incorrectly identified mark is ahazard, not an aid, to navigation.�

Alton B. Moody� � � � � � � � � � � � � � � � � � � � � �


Chapter 6 for additional perspectives applicableto ATONs as well as landmarks.) Numerous ref-erences are given at the end of this chapter forthose interested in additional detail. Namesenclosed in parentheses (e.g., Bowditch) denoteparticularly pertinent references. The Glossaryin appendix A provides definitions of key termsrelated to ATONs.

Brief Historical AsidesAs might be expected, what are now called

ATONs have a long history (see, e.g.,Bowditch, Naish). As the later history ofATONs may be familiar to readers of thismanual, it is interesting to provide some briefasides on the early periods. Towers (usedoriginally as landmarks, and later as light-houses) were reportedly constructed to aidpassage along the Mediterranean coast asearly as 660 B.C. Between 283 and 277 B.C.,Sostratus of Cnidus built a large (500 ft) struc-ture on the island of Pharos which markedthe harbor of Alexandria from the north. TheRomans established a network of fire towersalong the Mediterranean.

By medieval times, beacons and range mark-ers were in use to facilitate entrance to the portsof Genoa and Pisa. In the so-called Dark Ages inEurope, hermits and monks located on remoteislands and promontories displayed light signalsin chapels and participated in salvage operationsfor wrecked vessels. (Today this might be viewedas a conflict of interest!)

The organization of the Hanseatic League notonly provided for economic cooperation but alsoadvanced the use of ATONs (and mechanismsfor collecting what would now be termed �userfees�) for navigation. A surviving chart of the ap-proaches to Bruge dating from about 1500 A.D.shows buoys as well as towers. (A seaman�smanual of 1295 A.D. refers to buoys marking theriver channels to Seville.) In England, TrinityHouse was established in the early 1500s as apilotage authority charged with (among otherthings) the responsibility of constructing andmaintaining marks on the land.

By the 1700s ATONs had become relativelysophisticated and widespread. The first re-corded range marks in America were two lighttowers placed in line on Plumb Island to mark

the channel to Newburyport, MA, on theMerrimack River.

Importance of ATONs in CoastalNavigation

As with landmarks, ATONs are charted ob-jects used for determining LOP (e.g., with ahand-bearing compass or radar or by directplotting in the case of range markers) andcurves of position (e.g., circles of position withan optical range finder for ATONs with chartedheight information, such as certain lights or hy-perbolas of position with LORAN-C) so as todetermine a fix or estimated position for thevessel. ATONs also mark hazards to navigation,identify the limits to safe channels, designatespecial-use areas (quarantine and anchorages),and provide other relevant information. Table5�1 provides both general and specific illustra-tions of how information derived from ATONscan be used for marine navigation. ATONs canbe used to fix the vessel�s position, to serve ashoming or tracking aids, to ensure that the ves-sel remains clear of dangerous waters (e.g., byusing danger bearings, danger circles, or pass-ing on the �safe side� of buoys) to identify turnpoints, and for a variety of specialized purposessuch as compass calibration or (less frequentlywith ATONs) to determine whether or not thevessel�s anchor is dragging.

Importance of Positive Identification andRelated Matters

Before discussing the various types ofATONs, charting practices, and related mat-ters, it is appropriate to emphasize several keypoints noted throughout this manual.

The mariner should be fully famil-iar with the charting conventionsemployed to depict ATONs. And im-portant textual material (e.g., ChartNo. 1, and the appropriate USCGLight List) should be readily avail-able for reference.

Any observed ATON (or landmark)should be positively identified by themariner prior to its use for naviga-tion. Published texts (e.g., Cahill,


Milligan, Maxim) and USCG acci-dent files are replete with examplesof mishaps or accidents which re-sulted from the incorrect identifica-tion of an ATON. Bowditch (see ref-erences) lists �failure to identify aidsto navigation� as the second of 16common errors in navigation. Themere observation of an ATON (orlandmark) at approximately theright position and at approximatelythe right time�although relevant�is not sufficient proof that the aid ob-served is the same as that shown onthe chart. ATONs are equipped withnumerous characteristics (e.g., theflash characteristics and color of alight, the Morse code identifier of aradiobeacon, the number and colorof an unlighted buoy or daybeacon)to facilitate positive identification.

Closely related to the above point,it is important that charts (and suchpublications as the Light List andU.S. Coast Pilot) be amended as de-scribed in the latest published cor-

rections. ATONs are moved, renum-bered, removed, and/or characteris-tics changed periodically. This canhave significant consequences (seeCahill) for the uninformed mariner.Bowditch also lists �failure to cor-rect charts� among the common er-rors in navigation.

Whenever observations are taken onany fixed ATON or landmark, thisinformation should be plotted on thenautical chart by the mariner. Evena single LOP can be useful, and fre-quent fixes are typically necessaryin coastal waters where ATONs areplaced. Differences between thevessel�s dead reckoning position andthe plotted fix enable currents to beestimated and/or should alert themariner to the possibility of othererrors.

Finally, all available means (e.g.,maintenance of a dead reckoningplot, use of GPS, LORAN-C, depthsounder or other means) should be

Table 5-1Utility of ATONs Shown on Nautical Chart

GENERAL:

• Used for determining range or bearing by visual means (or radar) in coastal waters so as todetermine a fix or estimated position;

SPECIFIC ILLUSTRATIONS:

• Used for determination of fix, running fix, estimated position, set and drift of current;

• Used for plotting danger bearings, danger circles, horizontal danger angles;

• Used (in conjunction with danger bearing or circle) for evaluation of vessel’s position withrespect to unobservable hazards to navigation;

• Used to determine a safe course which avoids unobservable hazards to navigation;

• Used for establishing vessel turning bearings;

• Used for homing or tracking purposes;

• Used for compass calibration; and

• (Less frequently) Used for determining whether or not an anchor is dragging.


used for navigation. Reliance on onlyone method is unprofessional andunwise.

ATONs and Related Chart Information(General)

This chapter includes the followingATONs: lights, buoys, fog signals, daybeacons,ranges, and radiobeacons. These are discussedin order in the following sections. Brief com-ments on �trial courses� are also included inthis chapter. The symbols used in chartingthese aids are illustrated in Sections P, Q, R,and S of Chart No. 1, Nautical Chart Symbols,Abbreviations, and Terms (Ninth Ed.) to whichthe reader is referred. (Pertinent excerpts fromChart No. 1 are included in this chapter forready reference.)

ATONs are placed in appropriate locationsin harbors and inland waterways to facilitatenavigation. The placement of these ATONs fol-low a particular pattern or convention termedthe lateral system, in which the colors, shapes,and numbering of lights, buoys, anddaybeacons are determined by their positionin relation to �safe water.� (In virtually all U.S.waters the International Association of Light-house Authorities (IALA) System B is followed.Therefore, the IALA-B system is discussed inthis manual.) These designations are appliedto navigable channels proceeding from sea-ward toward the head (limit) of navigation. Thecolors and numbers of buoys and lights alongthe coasts and along traffic routes not leadingdistinctly from seaward or toward headwatersfollow the same system, but applied so thateven-numbered aids mark the starboard sidewhen proceeding in southerly direction alongthe Atlantic coast, in a northerly and westerlydirection along the gulf coast, and in a north-erly direction along the Pacific coast. Table 5�2 provides a capsule summary of the charac-teristics of lateral aid in most U.S. waters. Ad-ditional information on buoyage systems canbe found in the Light List and other references(e.g., Coast Guard Aids to Navigation,Chapman).

Most ATONs used by mariners on a day-

to-day basis for navigation purposes are main-tained by the USCG. In 1993, there were ap-proximately 50,500 federal ATONs in U.S. wa-ters (Ihnat)! These aids include lights, buoys(lighted and unlighted), daybeacons, and ap-proximately 200 marine radiobeacons. Asshown in figure 5�1, the majority (51 percent)of these ATONs are buoys�lights (25 percent)and daybeacons (24 percent) account for aboutequal portions of the remainder. (Fog signalsare not included in this tabulation, as theseare typically collocated with a buoy or light.)In addition to federally maintained ATONs,there are approximately the same number ofprivately maintained ATONs. Some privatelymaintained aids are useful for navigation andare tabulated in the Light List and shown onnautical charts. Charting federal aids (let alonesome fraction of the private aids) and keepingcharts up to date, is obviously a large under-taking.

An ATON is charted if it is in the LightList or is assigned a Light List number whenpublished in the LNM. Thus, any ATON found

SOURCE: USCG

Fig. 5-1. Distribution of the more than 50,500Federal ATONs in U.S. waters in 1993;

buoys are most numerous.

/,*+76 /,*+7('�%82<6

81/,*+7('�%82<6 '$<%($&216


in the Light List will also be found on the chart.1

Additionally, some ATONs are charted whichare not in the Light List, such as those estab-lished by neighboring foreign countries, aidshaving �reliable� maintenance authorities(such as those established by the military), andenvironmental buoys which are not included

in the Light List. As well, radar reflectors,lights, and sound signals are charted for thosefeatures (e.g., floats, targets, platforms, dredg-ing range markers, and data collection buoys)not specifically intended for use in navigation,whether the feature is listed in the Light Listor not.

Table 5-2Characteristics of IALA-B Lateral System

Characteristic

Color

Shape (buoys)

Daymark

Light color (when fitted)

Reflector color

Numbers (if numbered)

Port Hand Marks

Green

Cylindrical (can) or pillar

Green square

Green

Green

Odd

Starboard Hand Marks

Red

Conical (nun) or pillar

Red triangle

Red

Red

Even

At a point where a channel divides, when proceeding in the “conventional direction of buoyage,” apreferred channel in Region B may be indicated by a modified port or starboard lateral mark as follows:

Characteristic

Color

Shape (buoys)

Daymark

Color

Rhythm

Reflector color

Preferred Channel to Starboard

Green with one broad red horizon-tal band

Cylindrical (can) or pillar

Green square, lower half red

Green

Composite group flashing (2+1)

Green

Preferred Channel to Port

Red with one broad greenhorizontal band

Conical (nun) or pillar

Red triangle, lower half green

Red

Composite group flashing (2+1)

Red

CAUTION: When proceeding toward sea, it may not always be possible to pass on either side of preferredchannel aids to navigation. The appropriate nautical chart should always be consulted.

1This assumes that the chart has been corrected based upon data in the LNM.


ATON information provided on nauticalcharts includes a symbol unique to each classof aid and a set of characteristics such as num-ber, height, color, and nominal range. Thesecharacteristics are provided in labels. Symbolsand characteristics are placed so as to bereadily identified by the chart user (not ob-scured by less important information) and toavoid overlap with any charted channels.These standard symbols are reserved forATONs which appear in the Light List.Charted lights and beacons not intended asguides for normal surface navigation areshown with a landmark symbol (see NauticalChart Manual, Chapter 6. Landmarks) andidentifying label. Any identifying navigationallight or beacon that is not established by theUSCG or equivalent authority is identified onthe charts either by the label �Priv� (for pri-vately maintained aids) or by naming theagency that is responsible for its maintenance.

Temporary aids are seldom charted unlessgiven a Light List number. ATONs established(and/or aid characteristics that are changed)for the winter navigation season are consid-ered temporary aids and these (changes) arenot charted. However, specific details for im-portant aids, such as seasonal fog signals atmajor aids, are charted in all areas. A seasonalaid note is found on all Great Lakes charts andon east coast charts from Cape Henry, VA,northward. This note reads as follows:

SEASONAL AIDS

�During some winter months or whenendangered by ice, certain aids to navi-gation are replaced by other types orremoved. For details see the U.S. CoastGuard Light List.�

LightsAccording to official charting definitions

in the Desk Reference Guide, a light�

�is a luminous signal emitted by a fixedstructure2 to aid navigation that markschannels, warns of dangers or obstruc-tions to navigation, and assists themariner in determining his position.Lights are identified by their charac-teristics at night and by the shape andcolor of their daymarks. Light charac-teristics include flash sequence, lengthof light and dark periods, color, andrange of visibility. Lights are catego-rized by function (e.g., junction light,directional light, range light, leadinglight, sector light, passing light, andaeronautical light).� [Emphasis added.]

There were approximately 12,200 federallymaintained lights in U.S. waters in 1993.

Most lighted ATONs (including lights andlighted buoys) are equipped with controls thatautomatically cause the light to operate dur-ing darkness and to be extinguished duringdaylight. These devices are not of equal sensi-tivity and, in consequence, all lights do notcome on or go off at the same time. The light-ing apparatus is serviced at periodic intervals,but there is always the possibility that the lightis extinguished or operating improperly.

Lights can be used for navigation duringthe hours of daylight or darkness. During day-light, the fixed structures associated withthese lights serve as landmarks for bearingor range determination. During daylighthours, the identification of the light is basedupon the position of the light and its physicalappearance. (The physical appearance of a

2Lighted buoys are classified by NOAA as buoys, rather than lights, and are discussed later in the maintext.


light structure is not found on the chart, how-ever, as noted below.) At night, the light isused in much the same manner except that theidentification of the light is based primarilyupon the characteristics of the light, such asthe color, flash sequence, and position.

�Charting PracticesThis section provides information on chart-

ing practices for lights and related informa-tion. Charting conventions consist of a lightsymbol, associated labels and notes, and (forsectored lights or where lights have obscuredsectors) information on the sector(s).

�Symbol (P)Major lights, minor lights, and lighthouses

are charted as shown in Section P of Chart No.1. In particular, the position of the light isshown by a black 0.75 mm dot (or open blackcircle 1.0 mm in diameter in the case of an ar-ticulated light), with a magenta �flare� (3.4 mmin length with a rounded end of 0.6 mm ra-dius) drawn about 1 mm from the light dot.This light symbol has the visual appearanceof an exclamation mark (!) in print. The flareis generally oriented toward the label and isdrawn to avoid obscuring other relevant chartdetail. Where possible, the flare orientationis aligned with those of neighboring buoy sym-bols (see below). Leading lights (i.e., those ar-ranged, similar to range lights�except thatonly a single light is used�to indicate a pathto be followed) may be charted with the flareoriented seaward along the line.

�Labels and NotesThe label and note(s) provide information

on the name of the light and the light�s char-acteristics, including the light number (if any).This information is very useful for identifyingthe light and for determining whether it canbe seen from the vessel�s approximate posi-tion.

If the name of the light appears in the LightList and space permits, the name of the lightis shown in black conventional (vertical) typeabove the light characteristics.3 The name maybe omitted if it is the same as the name of thegeographic feature in the immediate vicinityand space is at a premium. Thus, for example,if the geographic name �Pt Judith� wereshown in the chart, the name �Pt Judith Lt�would not be given.

The characteristics of the light include itsflash characteristic, color, period, height, vis-ibility (nominal range), and number.

Flash characteristics include the sequenceand timing of the flashes and include fixed,occulting (single occulting, group occulting,and composite group occulting) isophase,

Miah Maull shoal light in Delaware BayOfficial U.S. Coast Guard photograph

3These are shown in conventional, rather than italic type because italic type refers, among other things, tofloating structures. See also Chapter 4.


f lashing (including single flashing, groupflashing, composite group flashing, quick,very quick, and ultra quick), Morse code (e.g.,Morse �A�), fixed and flashing, and alternat-ing. Illustrative flash characteristics and as-sociated chart labels are shown in Section P(10.1 to 10.11) of Chart No. 1, which is repro-duced in figure 5�2. Although not particularlycomplex, this diagram requires some study.Study of this illustration should be supple-mented with on-the-water practice in identi-fying the characteristics of lights. Marinersare also cautioned that if a vessel has consid-erable vertical motion due to pitching inheavy seas, a light sighted on or near the ho-rizon may alternately appear and disappearwith the possible result that its true charac-teristic will not be apparent. In consequence,the light could be misidentified. Under theseconditions, the true characteristic may not beapparent until the vessel is closer to the light.The watch stander should be placed at thehighest convenient station for such observa-tion.

The color of lights is shown using stan-dard abbreviation (e.g., R for red, G for green,W for white, etc., as shown in Sections P 11.2through 11.8 of Chart No. 1) following theflash characteristics of the light. Generally,white lights are not so labeled (and if no coloris shown, on the chart, white can be assumed)except where a light exhibits more than onecolor, in which case W is shown. Amber lightsare charted as yellow and abbreviated �Y.�Although the color of a light is important toits identification, mariners should be awarethat the apparent color of the light maychange with distance, because the variouscolored lights may have different nominalranges (see below). Additionally, ice or snowmay cover the panes of unattended lights,greatly reducing the visibility of lights (seebelow) and may cause colored lights to ap-pear white.

The period of a light is defined as the time

(in seconds) required to exhibit a full patterntogether with the interval between patterns.Periods are shown on the nautical chart, tothe nearest tenth of a second expressed as adecimal, after the flash characteristic. Mari-ners should �time� a light using a stopwatch.To increase the precision of measurement forlights with short periods, the aggregate timerequired to complete several cycles should bemeasured. Thus, for example, if 60 secondswere required for 10 cycles, the period wouldbe 6 seconds.

Taken together, the flash characteristic,color, and period provide key information nec-essary to identify the light when it is in opera-tion. According to both the Admiralty Manualof Navigation and Bowditch, the characteris-tics of a light must always be checked on sight-ing. As noted by Moody, �An incorrectly iden-tified mark is a hazard, not an aid, to naviga-tion.�

The height of the light is the vertical dis-tance between the light source (not the top ofthe light!) and the shoreline reference datum.Height is shown in feet using the abbreviation�ft� except on metric charts, where height isshown in meters using the abbreviation �m.�Height information is important for distance-off calculations (see Bowditch) in daytime orfor estimating the distance at which a lightcan be seen at night (see below). Normally, themariner should search for the highest lightsfirst when approaching a coast�as these arelikely to be seen most easily. However, themariner should bear in mind that lightsplaced at high elevations are more frequentlyobscured by clouds, mist, or fog than thoselights located at or near sea level.

The visibility of the light is expressed asthe �nominal range,� and is charted except inthe case of range lights or privately main-tained lights.4 The nominal range is the maxi-mum distance (in nautical miles on mostcharts, in statute miles on most Great Lakescharts) a light may be seen at night in clear

4The nominal range is not given in the USCG Light List either, because these are very short-rangeATONs.


Source: Chart No. 1.

Fig. 5-2. Illustrative Flash CharacteristicsContinued on next page

Light Characters

Light Characters on Light Buoys ~ Q

Abbreviation Class of light Illustration Period shown t----t

International National

10.1 F F Fixed

Occulting (total duration of light longer than total duration of darkness)

Single-occulting • • • • • Qc Qc; Qee

10.2 Qc(2)

Oe (2); Gp Qcc Group-occulting • • • • • • • • Example

Qc(2+3) Oc(2+3) Composite group-occulting • • • • • • • • Example

Isophase (duration of light and darkness equal)

10.3 Iso Iso; E Int Isophase

Flashing (total duration of light shorter than total duration of darkness)

FI FI Single-flashing

FI(3) 10.4

Example FI (2); Gp FI Group-flashing

FI(2+1)

Example FI (2+1) Composite group-flashing

10.5 LFI L FI Long-flashing (flash 2s or longer)

Quick (repetition rate of 50 to 79 - usually either 50 or 60 - flashes per minute)

a Q; Qk FI Continuous quick .. ,",.".,""',.,""

a(3) Q(3) Group quick 10.6

Example

la IQ; Int Qk FI; Interrupted quick I Qk FI

".,',..... "',.,"

F ,,---......

Qc; Qcc (,1""'1"""11""7,",,,)

Qc (2); Gp Oee ('(\'I""'"n"">I)

Oc(2+3) (",(\l"""1l"7n">l)

Iso; E Int (' '1""',., ...... '"">

FI (2); Gp FI errv-.....,

FI (2+1) err" ')j ,"~~AA"4-t

Q; Qk FI ~\\\"\lIIII'''lq0

IQ; Int Qk FI; I Qk FI

~\\"\\ J111f/q


weather (meteorological visibility of 10 nauti-cal miles) without regard for the height of thelight or the observer. For those lights with twoor more colors (see below) either both nomi-nal ranges are shown (e.g., 15/10M) or the lesserof the two ranges will be given.

Calculation procedures for estimating theactual distance from which a light can be seenat night, considering the height of the lightand observer, nominal range, and prevailingvisibility, are detailed in the Light List andother references (e.g., Bowditch, Dutton,Maxim). Common practice for the navigatoris to draw circles around these lights on thechart with radius equal to the distance atwhich the light is likely to be visible (seeSchlereth) and to estimate the correspond-ing time when these should first be seen.

Source: Chart No. 1.

ContinuedFig. 5-2. Illustrative Flash Characteristics

These calculations are only approximate(Burch). Nonetheless, if lights are not sightedwithin a reasonable time after that predicted,a dangerous situation may exist and the mari-ner should be appropriately cautious.

Finally, the assigned number or letter(s)of the light structure (if any) are shown fol-lowing the visibility, and enclosed in quota-tion marks. The number or letter can be ob-served (e.g., with binoculars) during daylighthours.

On large-scale charts, the characteristicsof lights are shown in the following order:flash characteristic, color, period, height, vis-ibility, and number. For example, an 85 footred light (number �2�) of nominal range 10miles which exhibits a group of three flasheswithin a period of 10 seconds would include


the light symbol, light name (if appropriate)and the label: Fl (3) R 10s 85ft 10M �2.�

Small-scale charts show complete informa-tion regarding characteristics for major sea-coast lights expected to be used for coastalnavigation, but may omit certain informationin cases where congestion is a problem. In thisevent, characteristics are omitted in the fol-lowing order: height, period, number of flashesin groups, the number or letter on the struc-ture, and the nominal visibility.

�Sectors, and Related MattersIn some cases, terrain masking (e.g., a

mountain or island) may limit the area overwhich a light may be seen. Knowledge of these�blind� areas is obviously useful to mariners.(There is, after all, no point in looking forsomething that cannot be seen. Moreover, aprudent mariner might well alter the in-tended track so as to avoid an obscured sectorof a major light.) An obscured sector (some-times termed �dark sector�) is a portion of thelight sector of a navigational light in which thelight is not visible. Where a LNM reports itsestablishment, the obscured sector (see Sec-tion P 43 of Chart No. 1) is charted with dashed�rays� marking the limits of the obscured sec-tor. Additionally a dashed arc in the sectorcentered on the light indicates the obscuredsector. Directional arrows are used to markthe points where the dashed arc intersects thedashed ray line. A label, �LT OBSC� or �DARKSECTOR,� is added for clarity. See figure 5�3for an illustration of a light with an observedsector taken from NOS Chart No. 13218.

In other cases, sectors are deliberately cre-ated by placing colored glass in the lanternsof lights to provide additional information tothe mariner. Sector lights (see Sections P 40and 42 of Chart No. 1 for symbology) are usedprimarily to warn mariners of dangerousshoals or other hazards to surface navigation.The danger sectors are usually red and arecharted (in degrees true) from the perspectiveof the mariner looking toward the light. Mari-ners are cautioned not to alter course basedsolely on the observed sectors, but rather tonote the correct compass bearing. This is be-cause it is difficult to determine the sector

boundaries with accuracy because the edgesof a colored sector cannot be sharply demar-cated.

Figure 5�4 presents an excerpt from NOSChart No. 12304 which shows a red sector onthe Brandywine Shoals Light warning ofshoals in this area.

�Directional LightsSeveral types of directional lights are in use

(see Section P 30 of Chart No. 1 for chart con-ventions). These lights have a very narrow sec-tor designed to mark a direction to be fol-lowed. The narrow sector may be flanked byan obscured or intensified light, or by lightsof a different color or characteristic. A direc-

Fourteen Ft. Bank Light in Delaware Bay.Note differences in appearance with

Miah Maull shown earlier.Official U.S. Coast Guard Photograph.


Fig. 5-3. Excerpt from NOS Chart No. 13218 (Martha’s Vineyard to Block Island). Note theobscured sector of the Gay Head Light south of Nomans Land. The light at Gay Head is an

alternating red and white with a period of 15 seconds and a nominal range of20 nautical miles. The height of this light is 170 ft.


Fig. 5-4. Excerpt from NOS Chart No. 12304 (Delaware Bay). Note the red sector ofthe Brandywine Shoal Light. The 60 ft. light has a nominal range of 13 nautical miles.Reference to the Light List indicates that this is the lesser of the 17-mile range of the white

light and the 13-mile range of the red sector. The horn, according to the Light List, emits a 2-second blast every 15 seconds. The light is a group occulting with a 12-second period. Note

also the riprap symbol at the base of the light.


tional light normally shows three adjoiningsectors of red, white, and green, with the cen-ter white beam oriented to mark the channel.

�Leading LightA leading light (see Section P 20 of Chart

No. 1 for chart conventions) is similar to arange light or marker (see below) except thatit marks a channel with a single light (withray lines) rather than with two separate lights.It is usually a high intensity beam marking thesafe channel which diminishes to much lowerintensities around the remainder of the hori-zon. It differs from a directional light (seeabove) in that it shows only one color of lightinstead of the three-color sectors of the direc-tional light.

�Aeronautical LightsAeronautical lights (see Section P 60 of

Chart No. 1 for chart conventions) are whiteand green navigation lights associated with air-ports and often found atop the control tower.Because these are generally attended duringtheir hours of operation, the lights are highlydependable. Moreover, these are often the mostconspicuous of the nonstrobe lights and theirnominal range may be greater than those es-tablished for marine navigation. The aeronau-tical light is charted by a standard light dotwith magenta flare. The light symbol is accom-panied by its characteristics and the label�AERO.�

�Articulated LightsAn articulated light is a floating light, also

called a buoyant beacon. It is basically a verti-cal pipe structure that oscillates around a uni-versal coupling connected to a sinker. The lightstructure (which is typically 10 feet to 15 feet

above the water surface at high tide) is keptupright by the buoyancy of a submerged floata-tion chamber. Unlike other buoys (see below)it has no �scope� of chain and the light is di-rectly over the sinker, i.e., this structure hasno �watch circle.� It is designed primarily tomark narrow channels with greater precisionthan conventional buoys in situations wherethe depth of water, up to 60 feet, is too greatfor a normal pile or dolphin light structure (seeDutton).

When first introduced, this type of ATON,which is neither a true buoy nor exactly a fixedlight, required a new symbol for charting (seeSection P 5 of Chart No. 1). This symbol is ablack open circle 1.0 mm in diameter (the �ap-proximate position� symbol for a landmark ex-plained in Chapter 6) centered on the pub-lished position with a magenta flare. The opencircle is chosen in lieu of a dot (used for otherfixed lights) because the structure may be dis-placed more than 10 feet of its �true� position.The articulated light is labeled �Art� in New-ton Medium italic type.5

�Strobe LightsMany charted features are marked with

very quick-flashing high-intensity lights,called strobe lights. The light is usually a xe-non gas condenser-discharge flash lamp orflash tube. Strobe lights are used on certainUSCG-maintained ATONs and on aeronauti-cal hazards, such as stacks, towers, and build-ings. ATONs published in the NM and LightList as well as landmarks with a strobe lightinclude the label �Strobe� as well as other la-bel elements (see above). The flash period of astrobe light is usually (but not always) omit-ted because of its extremely short duration(much less than 1 second).

5The reason italics are used (in lieu of the vertical lettering found on other lights) is that articulatedlights�though classified as fixed structures�are floating lights. Buoys are also labeled in italic type.


�RiprapRiprap are mounds of broken rock, cobbles,

boulders, or fragments that are often placedaround light structures as protection againstice damage and scouring by fast-moving cur-rents. Desirable as the use of riprap may befrom the point of view of protecting the struc-ture�and helping to ensure the reliability ofthe light�riprap also presents a hazard tonavigation for vessels that pass too closeaboard. Riprap is denoted on nautical chartsby a special symbol (see Section P a of ChartNo. 1).

Supplemental Information RegardingLights and Other ATONs

In addition to the nautical chart, the LightList, the U.S. Coast Pilot, and commercialcruising guides offer relevant information onATONs. Additional information provided inthese sources is briefly discussed below.

�The Light ListThe Light List is the authoritative source

of information on ATONs. It is published an-nually by the USCG in several volumes, cov-ering various geographic areas. The Light Listis a valuable complement to the nautical chartand provides specific information on ATONs.Contrary to the implication of its title, theLight List offers information on unlighted aswell as lighted ATONs. In addition to generalinformation regarding ATONs the Light Listincludes specific information on each ATONsuch as its LLNR, the name and location of theATON, the geographic coordinates (latitudeand longitude), characteristics, height, nomi-nal range (for a wider variety of ATONs thanfound on the nautical chart), an identificationof the structure, and pertinent remarks.

The organization of the Light List is actu-ally quite logical, but requires some study tobe used effectively. When all else fails, the

index at the back of each volume is helpful.Much of the information on ATONs shown

in the Light List is identical to that providedon nautical charts. However, the Light Listdoes contain information not found on chartsand, additionally, is revised more frequentlythan most nautical charts and, therefore, ismore likely to contain up-to-date information.(However, a properly corrected chart is alsoup to date.)

Perhaps the most useful information con-tained in the Light List that does not appearin the nautical chart is a brief description ofthe structure and the accompanying remarks.The description of the structure is particularlyuseful for identifying lights during daylightconditions. For example, the route from sea-ward up the Delaware Bay is marked by sev-eral lighthouses, including the BrandywineShoal Light (see figure 5�4), Fourteen FootBank Light, Miah Maull Shoal Light, Elbow ofCross Ledge Light, and Ship John Shoal Light.(Photographs in this chapter show two of theselights.) Mariners with local knowledge canreadily identify these lights by their distinc-tive physical appearance. 6 However, thosewithout local knowledge would certainly ben-efit from the following descriptions taken fromthe Light List, Volume II, Atlantic Coast, TomsRiver, New Jersey to Little River, South Caro-lina (1993):

�Brandywine Shoal Light-Cylindricalconcrete structure, adjacent to oldscrewpile with red sector from 151 de-grees to 338 degrees covering shoalarea southwest of Cape May. As withseveral other lights in the area, thislight is equipped with an emergencylight of lower intensity with same char-acteristic as main light when main lightis extinguished.

6In SAR cases on the Delaware Bay in which the distressed mariner reports a position near one of theselights, rescue authorities often ask the mariner to describe the light. This procedure can save fruitless searchhours in cases where the distressed vessel does not have an accurate position fix and misidentifies the light.


�Fourteen Foot Bank Light-Whitetower and dwelling on black cylindri-cal pile.

�Miah Maull Shoal Light-Red conicaltower, on gray conical pier; red cylin-drical watch room and black lantern.

�Elbow of Cross Ledge Light-Red skel-eton tower with small white house oninternational orange cylindrical base.

�Ship John Shoal Light-Brown octago-nal dwelling with pyramidal roof; oncylindrical pier. Light has red sectorfrom 138 degrees to 321.5 degrees cov-ers shoals on east channel. High inten-sity beam down Miah Maul Range.�

Additionally, the Light List provides spe-cific information on ATONs which are sea-sonal�information not shown on the nauticalchart. For example, this same volume of theLight List notes that the Deadman ShoalLighted Buoy IDS which is normally equippedwith a flashing green light with a 4-secondperiod is replaced by an unlighted wintermarker from December 15 to April 1 of eachyear.

�The U.S. Coast PilotThe U.S. Coast Pilot also provides infor-

mation on lights and other ATONs. The scopeof the material provided in the U.S. Coast Pi-lot is quite broad (see other chapters of thismanual) and, as a result, coverage of ATONsis less complete than can be found in the LightList. Nonetheless, the U. S. Coast Pilot doescontain useful information on selected ATONs.In particular, the U. S. Coast Pilot often pro-vides descriptions of lights that are useful foridentifying the light structure during daylighthours. For example, here are a few descrip-tions of lights taken from the U.S. Coast PilotVolume 3 (1993), Atlantic Coast: Sandy Hookto Cape Henry:

�The entrance to South River is be-tween Saunders Point and ThomasPoint, 1.8 miles northeastward.Thomas Point Shoal Light (38° 53.9'N, 76° 26.2' W), 43 feet above thewater, is shown from a white hex-agonal tower on piles, in depths of5 feet near the outer end of the shoal1.2 miles east-southeastward of thepoint; a fog signal is at the light. Thelight is 1.5 miles due west of a pointon the bay ship channel 124.2 milesabove the Capes.� (p. 176)

�Solomons Lump Light (38° 02.9' N,76° 00.9' W), 47 feet above the wa-ter, is shown from a white octago-nal dwelling, with a square tower,on a brown cylindrical base, indepths of 7 feet on the Smith Islandside of Kedges Straits.� (p. 190)

�Sharps Island Light (38° 38.3' N,76° 22.5' W), 54 feet above the wa-ter, is shown from a leaning, browntower on a cylindrical pier, in 10 feetat the north end of a shoal thatbares at the east end�.� (p. 194)[This description is particularlyvaluable to those without localknowledge. The structure actuallyleans a great deal, and it is difficultto believe that this is an ATONwhen approaching from certainangles in daylight!]

�Published Guides and Other BooksPublished cruising guides and other books

often have descriptions and photographswhich are useful to the mariner. Books onlighthouses (e.g., Caldwell, de Gast, Holland),in particular, often contain photographs whichfacilitate daylight identification. These booksare not designed for navigational purposes,however, and the appearance of the light mayhave changed since the photograph wastaken.7


BuoysAccording to the somewhat lengthy of-

f ic ial def init ion in the Desk Re ferenceGuide, a buoy�

�is a floating object, other than alightship, moored or anchored to thebottom as an aid to navigation. Buoysmay be classified according to shape,as spar, cylindrical or can, conical, nun,spherical, barrel, or pillar buoy. Theymay also be classified according to thecolor scheme, as a red, green, or check-ered buoy. A buoy fitted with a charac-teristic shape at the top to aid in itsidentification is called a topmark buoy.A sound buoy is one equipped with acharacteristic sound signal, and may befurther classified according to the man-ner in which the sound is produced, asa bell, gong, horn, trumpet, or whistlebuoy. A lighted buoy is one with a lighthaving definite characteristics for de-tection and identification during dark-ness. If the light is produced by gas itmay be called a gas buoy. A buoyequipped with a marker radiobeacon iscalled a radiobeacon buoy. A buoy withequipment for automatically transmit-ting a radio signal when triggered byan underwater sound signal is called asonobuoy. A combination buoy has morethan one means of conveying intelli-gence; it may be called a lighted soundbuoy if it is a lighted buoy provided witha sound signal. Buoys may be classifiedaccording to location, as channel, mid-channel, middle ground, turning, fair-way, bifurcation, junction or sea buoy.A bar buoy marks the location of a bar.

A buoy marking a hazard to navigationmay be classified according to the na-ture of the hazard, as obstruction,wreck, telegraph, cable, fish net, dredg-ing, or spoilground buoy. Buoys usedfor particular purposes may be classi-fied according to their use, as anchor,anchorage, quarantine, mooring, warp-ing, swinging, marker, station, watch,or position buoy. A light-weight buoyespecially designed to withstandstrong currents is called a river buoy.An ice buoy is a sturdy one used to re-place a more easily damaged buoy dur-ing a period when heavy ice is antici-pated.�

The above definition also identifies someof the many navigational uses of buoys. Per-haps the most significant use of a buoy is toenable the mariner to stay in safe water andavoid unseen hazards to navigation.

As noted, buoys are the most commonATON. Approximately 25,500 federal buoysmarked U.S. waters in 1993. Buoys may belighted and/or have fog signals (see below),but most (82 percent) are unlighted can or nunbuoys.

Physically, buoys are floating ATONs thatare moored to the seabed by concrete sink-ers attached to the body of the buoy withchain or synthetic rope of various lengths.Buoy moorings vary in length, being suffi-ciently long to accommodate the water depthwhere the buoy is located, plus an allowancefor variations in water depth. The mooringlengths define a �watch circle,� and buoysmove within this circle depending upon wind,current, and tidal height. The size of thewatch circle is not reflected in the chart.

7As an example of this point, an attractively illustrated book (see de Gast) reprinted in 1993, contains adramatic photograph of the Sharps Island Light referred to above. This light (correctly described in the USCGLight List) is leaning as a result of ice damage in 1977. The photograph of this light, unchanged since theoriginal 1973 edition of this book, does not reflect this damage. No doubt the light looks better in its undamagedstate, and the author did not intend to write a navigation text.


ner should try to avoid fixing the vessel�s posi-tion using floating aids.8 As noted in the intro-ductory material published in each Light List:

�Buoy positions represented on nauticalcharts are approximate positions only,due to the practical limitations of posi-tioning and maintaining buoys and theirsinkers in precise geographical locations.Buoy positions are normally verifiedduring periodic maintenance visits. Be-tween visits, atmospheric and sea condi-tions, seabed slope and composition, andcollisions or other accidents may causebuoys to shift from their charted loca-tions, or cause buoys to be sunk or cap-s ized�.

�Prudent mariners will usebearings or angles from fixed aids to navi-gation and shore objects, soundings, andvarious methods of electronic navigationto positively fix their position.� [Empha-sis added.]

Guidance on the use of buoys for position fix-ing offered in COMDTPUB P16502.8, U. S. CoastGuard Aids to Navigation (p. 39) is even moreexplicit:

�In order for mariners to derive maxi-mum use from aids to navigation, thedifferent aids to navigation are shownon nautical charts. Thus, mariners areaware of the aids to navigation whichthey may expect to pass, and may plotany bearings which they take for thepurpose of determining their position.DO NOT USE BUOYS TO PLOT A FIX.�[Emphasis in original.]

More than 80 percent of buoys in U.S. watersare unlighted. Unlighted nun buoy.

Official U.S. Coast Guard photograph.

Buoys vary substantially in size and physi-cal appearance. The reader is directed to anyof several references at the end of this chap-ter for illustrations and photographs of vari-ous types of buoys.

�A Brief Digression: Position Fixing withBuoys

It is noted above that ATONs can be usedfor fixing the vessel�s position. Although it maybe common practice to use both fixed and float-ing ATONs for this purpose, the prudent mari-

8An articulated light (see main text) is a buoyant structure tethered directly to the seabed in such amanner that it has no �watch circle.� Although similar to a buoy in some respects, it is regarded as a fixedATON for charting purposes. However, these should be treated as floating aids in terms of position fixing.


Buoys could be off-station at any time, butare more likely to be off-station after storms,and in icy conditions. During the severe flood-ing of the Midwest in the summer of 1993, forexample, it was estimated (Professional Mari-ner, Issue No. 3) that as many as 70 percent ofthe thousands of ATONs in the area neededto be replaced. Severe ice and snow storms inthe Northeast in the following year also re-

quired numerous buoys to be reset in the Dela-ware Bay and New York harbor.

It is recognized that there are circum-stances where fixed ATONs may not be avail-able for position fixing yet numerous buoysmight be present in the area. Any positionbased solely on buoys should be regarded witha healthy skepticism and verified using fixedATONs at the first opportunity.

Buoys can be damaged and moved off station by ice, one of the reasonsthat position-fixing with buoys is not recommended. Here crew from the

USCG Red Oak work on an ice-damaged buoy.Official U.S. Coast Guard photograph.


�Charting PracticesAs with other ATONs, buoys are charted

with a symbol and one or more labels provid-ing capsule information about the buoy. Asnoted, generally only buoys listed in the LightList are charted. In most cases this presentsno difficulty for the mariner. However, thereare numerous buoys that are not charted. Inparticular, buoys marking channels along theAtlantic coast and gulf coast that shift fre-quently are generally omitted. (Charting thesewould require excessively frequent revisions.)Where these buoys are not charted, a note isadded explaining that these buoys are omit-ted. In this case a standard note is added tothe chart:

Entrance to Inlets

The entrance channels at the inlets notprotected by jetties are subject to fre-quent changes. The buoys are notcharted because they are frequentlyshifted in position. Buoys are removedif shoaling makes inlets unnavigable.

Entries for such buoys in the Light List donot contain latitude and longitude coordinates.

Note also that a given chart may omitbuoys (and other information) which areshown on a larger scale chart of the area.

�Symbols (Q)

Glossary in appendix A of this manual and theLight List . Additionally, the Light List pro-vides an explanation of the significance of eachbuoy to the mariner.

The position of a buoy is shown with asmall circle, the �approximate position� sym-bol (see Chapter 6) because of the practicallimitations in positioning and maintainingbuoys and their sinkers in accurate geo-graphic locations. Buoys are charted, insofaras possible, in their published position onlarge-scale charts. In cases where a buoy po-sition coincides with the symbol for anothercritical feature, such as a rock awash, thebuoy may be charted slightly off position forclarity, but always on the same azimuth asthe feature that it marks. If buoys are on op-posite sides of a dredged channel and plotless than 0.5 mm apart, the aids may be sepa-rated to 0.5 mm.

Channel buoy symbols (e.g., the diamondshape) are generally shown at a 65° angle fromthe channel lines, with the symbol pointing to-ward the top of the chart. Buoy symbols mark-ing the limits of fish trap areas are orientedso as to fall inside the area. For other buoysthe orientation of the buoy symbols is approxi-mately 25° from the vertical with the symbolinclined toward the label.

Lighted buoys, except superbuoys, arecharted with a magenta disk 2.5 mm in diam-eter, centered on the circle located at the baseof the buoy symbol. The few buoys equippedwith a RACON9 are charted with a 7.1 mm di-ameter magenta circle centered on the circlelocated at the base of the buoy.

Superbuoys, including single point moor-ing buoys, oceanographic data acquisition sys-tems buoys (ODAS), and large automated navi-gation buoys (LNB or LANBY), share a uniquesymbol (Sections P 8 and Q 26 of Chart No. 1).See figure 5�6 for an illustration.

There are numerous charting symbols usedto depict buoys of various types. Figure 5�5,taken from Chart No. 1, provides a sample forreview. Chart No. 1 should be studied in somedetail to ensure familiarity with the variousbuoy symbols. Refer to table 5�2 for guidanceon the significance of lateral aids. Definitionsof various types of buoys can be found in the

9The word RACON is derived from RAdar beaCON. A RACON produces a coded response (Morse) whentriggered by a radar signal.


Fig. 5-5. An Excerpt From Chart No. 1: BuoysContinued on next page

Buoys and Beacons

IALA Maritime Buoyage System, which includes Beacons ~ Q 130

1 0 Position of buoy ~

Colo rs of Buoys and Beacon Topmarks

Abbreviations for Colors ~p

2 ' G , .. 1 Green and black A A A • 1 G B G G G

3 f '~" 0 ~ 1 Single colors other than green and black -6 4 Q J 1 R R Y Y R

4 ' RG .. • 1 1 Multiple colors in horizontal bands, the color J 1 sequence is from top to bottom A BY GRG BRB

5 1; ~ (l) .1 1 Multiple colors in vertical or diagonal stripes, 1 1 the darker c%r is given first 161 RW RW RW

6 Retroreflecting material

Note: Retroreflecting material may be fitted to some unlit marks. Charts do not usually show it. Under IALA Recommendations, black bands will appear blue under a spotlight.

Lighted Marks

Marks with Fog Signals ~ R

7 ~ ~ .Lt Lighted marks on standard charts AFI.G ! FI.R , , ~G , R

8 Lighted marks on multicolored charts .l;';lFI.R 161150 !FI.G , R

RW , G Topmarks and Radar Reflectors

For Application of Topmarks within the IALA-System ~ Q 130 T opmarks on Special Purpose Buoys and Beacons ~ Q

• .. o .. : 0 X I ! , I I .. . 0 .. p

9 .. .. , , IALA System buoy topmarks .. , , .. , , .. (beacon topmarks shown upright) , , .. {l , to 13 1r

10 Beacon with topmark, color, radar reflector and

(lN02 designation Name

R

11 ~ 1 Buoy with topmark, colo r, radar reflector and designation ~ AN03 G

Note: Radar reflectors on floating marks are usually not charted.


ContinuedFig. 5-5. An Excerpt From Chart No. 1: Buoys

Buoys Features Common to Buoys and Beacons ~Q1-11

Shapes of Buoys

20 fiN D Conical buoy, nun buoy 4

21 lIc I;;J. Can or cylindrical buoy .l;1

22 ~sp £:) Spherical buoy .Q

23 lip .Lt Pillar buoy Ll

24 lis j Spar buoy, spindle buoy 1

25 II JI;l Barrel buoy 11;)

26 k~ Super buoy -6

Light Floats

FI.G.3s

30 ~, Light float as part of IALA System ~Z~':e • G~

31 Light float (unmanned light-vessel) riP FI.10s12m26M not part of IALA System ,

Mooring Buoys

Oil or Gas Installation Buoy ~L Small Craft Mooring ~U

40 .. Mooring buoys A .4 .d .. 41 .. Lighted mooring buoy (Example) .4 FI.Y.2,5s

No1 , "

~ r ~ \ :

Trot, mooring buoys with ground \ : / 42 tackle and berth numbers ·----CD----~----®---~

, I \ , , '

.i 1 ~

43 See Supplementary national symbols s. t Mooring buoy with telegraphic or telephonic communication .4JVVVVVVVVVVVVVV

------------.., I

44 Numerous moorings (example) Small Craft I Moorings I

I --------------1


As a point of interest the presentLANBYs�built originally to replacelightships�are now nearing the end of theirservice life and are being replaced by smaller,solar-powered exposed location buoys (ELBs).The newer ELBs are cheaper to buy and main-tain than the older diesel-powered LNBs(Walsh).

�Charted CharacteristicsThe character i s t i cs o f buoys inc lude

color and shape, and, i f so equipped, thecolor and period of their light. Character-ist ics are abbreviated as shown in Chart

No. 1 (Sections Q 2 through Q 71, and athrough U) and the Light List. These char-acter is t ics are important to the marinerfor identification purposes. Indeed, as withlights, all mariners are cautioned to estab-lish positive identification of each buoy inthe vicinity of the vessel�s track. Notice-ably absent from this l ist of characteris-t ics are the height o f the buoy and thenominal range ( i f l ighted) . (Nominalranges for selected buoys can be found inthe Light List , and typical ly varies fromabout 4- to 6-nautical miles for most lightedbuoys.)

LANBY silhouetted against rising sun.Official U.S. Coast Guard photograph.


spherical buoy, spar buoy, or pillar buoy) andby any audible signal they emit (bell, whistle,gong). Buoys (with the exception of mooringbuoys) are labeled as to their color using speci-fied abbreviations given in Chart No. 1.11 Forexample, red buoys are shown with magentafill, labeled �R,� and green buoys with greenfill and labeled �G.�

The identifying number (or letter(s))painted on the buoy (not the LLNR) is shownin quotation marks, e.g., �22.�

Light characteristics and period are alsopresented in the label in much the same man-ner as noted above for lights.

Private buoys listed in the Light List areidentified with the label �Priv� in italic print.The service name is charted on militaryATONs, e.g., �Navy.� Privately maintainedbuoys not listed in the Light List are not gen-erally charted.

A radar-enhancing structure or reflectivematerial has been installed on nearly all ma-jor buoys and many minor buoys. Therefore,reference to this feature is not charted as partof the buoy�s characteristics. Instead, the fol-lowing note is included on the chart:

�Radar reflectors have been placed onmany floating aids to navigation. Indi-vidual radar reflector identification onthese aids has been omitted from thischart.�

On large-scale charts, the characteristicsof buoys are shown in the following standard-ized order; color (omit if black) shape, (if un-lighted), number (or letter(s)), flash character(if lighted), light color (if lighted), light period(if lighted), and fog signal (if so equipped). Forexample, the complete legend would becharted as follows:

10This is consistent with the convention that floating objects are shown in italics.11Black buoys are not discussed in this manual as these are being phased out.

Fig. 5-6. Excerpt from NOS Chart No. 12214 (CapeMay to Fenwick Island). Note the LANBY in thisillustration. This buoy has a RACON with theidentifier (— —) as well as a light and a horn.

Buoy characteristics are shown in italictype.10 These labels are placed so as not tooverlap with wreck symbols, shoals, leastdepths, and other critical features. Buoys areidentified on charts by their shape (can, nun,


Lighted Buoy Unlighted Buoy

R �22� RFl R 4s BELL N �22�

In congested areas and on smaller scalecharts, some of these characteristics are some-times omitted. Characteristics of lighted buoysare omitted in the following order: period,color, number, light color, and flash charac-teristics. For unlighted buoys, the correspond-ing order is: color then number.

Space constraints do not permit an exhaus-tive discussion of the many types of buoysfound in U.S. waters. However, three of themost common types of buoys are briefly re-viewed.

�Channel BuoysThese buoys mark the edges of navigable

channels. In the IALA-B system, red buoysmark the starboard side of the channel, andgreen the port side of the channel when pro-ceeding from seaward. Unlighted red buoyshave a conical shape, called a nun, and beareven numbers, increasing from seaward. Thesewould be charted using the first symbol shownin Section Q 3 (Q 20) of Chart No. 1 and carrythe label R (for red), N (for nun), and the num-ber of the buoy (e.g., �6�) in quotation marks.If lighted, this buoy would have a somewhatdifferent physical appearance (e.g., a largerbuoy rather than the simple nun), a red lightatop the buoy, and would be charted by add-ing the magenta disc and the characteristicsof the light would be noted as discussed above.

Unlighted green buoys have a cylindricalshape, called a can, and bear odd numbers, in-creasing from seaward. These would becharted using the first of the symbols shownin Section Q 2 (Q 21) of Chart No. 1, and carrythe label G (for green), C (for can), and thenumber of the buoy (e.g., �7�) in quotationmarks. If lighted, this buoy would have a some-what different physical appearance (e.g., alarger buoy rather than the simple can), agreen light atop the buoy, and would becharted by adding the magenta disc and the

characteristics of the light would be noted asdiscussed above.

Incidentally, mariners are sometimes con-fused by the exact meaning of the phrase �re-turning from seaward� in certain instances.The nautical chart should always be consultedto verify the safe side for passing any buoy withlateral significance. Additionally it is worthnoting that no buoy should be passed veryclose aboard; buoys can move throughout thewatch circle (endangering the vessel). More-over, buoys may be located outside of the chan-nel (generally noted in the Light List) in caseswhere the channel is deep. A vessel that ven-tures too close to the buoy may no longer be inthe channel.

A Standard Lighted Radar Reflective Buoy(no sound).

Official U.S. Coast Guard Photograph.


�Junction BuoysJunction buoys typically mark a junction

of two channels and can be passed safely oneither side. As with other buoys, these can belighted or unlighted.

If unlighted, the buoy would re-semble a green can (if the preferredchannel were to the right when ap-proaching from seaward) or a rednun (if the preferred channel wereto the left when approaching fromseaward). The nun would have hori-zontal red and green bands with thetopmost band red. It would becharted by the symbol shown in Sec-tion Q 4 of Chart No. 1. The diamondshape would have two fills�red andgreen (topmost red)�and the let-ters RG along with the letter(s) onthe buoy shown in quotation marks.

If lighted, these would be largerbuoys, but retain the same physicalcolor and lettering scheme. Thecolor of the light matches the colorof the topmost band. These wouldbe charted using the same symbolsas given above, except that the ma-genta disc would be added, alongwith the light characteristics asnoted above.

�Midchannel BuoysMidchannel buoys (also called fairway

buoys) mark safe water at or near the centerof the channel and can be passed on eitherside. Physically these can be lighted (with awhite light blinking the Morse �A�) or un-lighted, with either the characteristic shapeof the lighted buoy or a spherical shape. Theseare vertically striped red and white. These arecharted by the first of the symbols shown inSection Q 5 of Chart No. 1, with or withoutthe magenta disc depending upon whether thebuoy is lighted or not. The label would con-tain the color code RW (for red and white), andthe identifying letter on the buoy, togetherwith the light characteristic Mo (A) if appro-priate.

Fog Signals (R)According to official charting definitions

in the Nautical Chart Manual, fog signals�

�are audible aids used to warn of dangerand to provide the mariner with a meansof determining a craft�s position when vis-ibility is obscured by fog, snow, rain,smoke, or thick weather. Among the de-vices in common use as fog signals are thefollowing:

�Diaphones produce sound by means ofa slotted reciprocating piston actuatedby compressed air. 'Two-tone' blastsconsist of two tones of different pitch,beginning with a high-pitched blast andending on a low pitch.

�Diaphragm horns produce sound bymeans of a disc diaphragm vibrated bycompressed air or electricity. Duplexor triplex horn units of differing pitchproduce a chime signal.

�Sirens produce sound by means of ei-ther a disk or a cup-shaped rotor actu-ated by compressed air or electricity.

�Whistles produce sound by com-pressed air emitted through a circum-ferential slot into a cylindrical bellchamber.

�Bells produce a distinctive sound bythe vibration of a hollow, cup-shapedmetallic vessel which gives forth a ring-ing sound when struck.

�Gongs produce a sound by the vibra-tion of a resonant disc.�

There were approximately 1,620 fog sig-nals on federally maintained ATONs in 1993,the majority (75 percent) of which were in-stalled on buoys.

These fog signals are used by the marinerin much the same manner as lights or buoys.And, indeed, these signals are often collocatedwith fixed or floating aids to navigation. Each


fog signal has specific characteristics by whichit can be distinguished. The signal character-istic is the phase relationship of the recurringsound emissions. Here are a few pointers tokeep in mind relative to fog signals and op-eration in fog:

Fog signals on fixed stations andlarge navigational buoys produce aspecific number of blasts and silentperiods each minute, when operat-ing, to facilitate positive identifica-tion.

Fog signals on buoys are generallyactivated by the motion of the sea:therefore, they do not emit regularsignal characteristics and, whenthe sea is calm, may emit no soundsignals.

Fog signals can be activated by sev-eral means (including manually, re-motely, or with a �fog detector�). Incases where a fog detector is em-ployed, there may be a delay in theautomatic activation of the signal.Additionally, fog detectors may notbe capable of detecting patchy fogconditions.

The sound from a fog signal may notbe sufficiently loud to be heard overthe noise of an engine. Therefore,it may be useful to periodically re-duce the engine to idle power�orturn it off completely�to listen forthese signals.

Remember to sound the appropri-ate signals when operating in fog.If visibility is so impaired to neces-sitate reliance on fog signals, it issufficiently poor to require appro-priate sound signals from all ves-sels. Note also that speed shouldalso be adjusted to the prevailingcircumstances.

Particular attention should be paidto positive identification of buoys insequence. When a buoy in sequenceis missed, consider running asearch pattern to find the buoy.Moreover, use all available meansof navigation, including electronicposition-finding aids, radar, anddepth-sounder information.

Finally, as noted in the Light List,�mariners should not rely onsound signals to determine theirposition. Distance cannot be accu-rately determined by sound inten-sity. Occasionally, sound signalsmay not be heard in areas close totheir location. Signals may notsound in cases where fog existsclose to, but not at, the location ofthe sound signal.�

These important caveats aside, fog signalscan be very useful aids to navigation in cir-cumstances of restricted visibility.

�Charting PracticesFog signals are depicted by a symbol and

appropriate labels and notes. In most cases,fog signals are located on fixed or floating aidsto navigation. Therefore, the fog signal ischarted using the appropriate symbol for thelight or buoy. Information on the fog signal isincluded in the labels associated with theATON. In some cases, fog signals are includedon structures not normally used for naviga-tion. In this case the landmark symbol (seeChapter 6) is used, and the appropriate labelappended.

�Labels and NotesFog signals are labeled as �DIAPHONE,�

�HORN,� �SIREN,� �WHISTLE,� �BELL,� or�GONG.� The appropriate designation (seeSection R of Chart No. 1) is used as part of thecharacteristic of the aid. Refer to the Light Listfor a detailed presentation of the sound se-quence and period.


12According to Naish (see references), the word beacon comes from the German word bake. The meaning ofthis word in Frisia and North Germany is a signal pole or construction placed in or near the water. The pluralform, baken, is the source of the English word beacon.

U. S. Coast Guard ATON personnel servicing daymark and light, Miami, Florida.Official U.S. Coast Guard Photograph

Daybeacons (Q)According to official charting definitions in

the Desk Reference Guide, a daybeacon�

�...is an unlighted fixed aid, specificallydesignated for navigation, placed onshore or on marine sites. They are es-tablished and maintained by the U.S.Coast Guard. They are identified bytheir color and the shape of thedaymark. Reflective borders are placedon certain daybeacons to assist the

navigator using a searchlight to morereadily locate them at night. The colorof the reflectors has the same signifi-cance as the color of the aid.� [Empha-sis added.]

Key words in the above definition are �bea-con� and �fixed.� Contrary to the popular senseof the word �beacon,� daybeacons are un-lighted aids.12 Moreover, these are fixed struc-tures and, therefore, admonitions against


using floating structures (noted in the abovesection on buoys) for position fixing do notapply. Daybeacons are used by mariners in thesame manner as lights and landmarks�e.g.,to identify channels and to fix the vessel�s po-sition. The lack of lighting limits the utility ofthese aids for night navigation but, despite thislimitation, daybeacons appear surprisinglybright in the reflected glare of the vessel�ssearchlight. Daybeacons include lateraldaybeacons (in red or green), preferred chan-nel daybeacons, safe water daybeacons (in red-and-white), and special-purpose daybeacons(yellow quarantine area daybeacons, regula-tory warning daybeacons).

There were approximately 11,900 federallymaintained daybeacons in U.S. waters in 1993,less than one-half the number of buoys.Daybeacons are often used in shallow inlandwaters, because these are less expensive to in-stall and maintain than buoys. Additionally,these have the advantage of being fixed, ratherthan floating structures. Physically, these con-sist of one or more piles driven into the bot-tom, surmounted by signboards calleddaymarks.


ing practices for daybeacons and related in-formation. Charting conventions consist of asymbol and associated labels to describe thecharacteristics of the daybeacon.

�Daybeacon SymbolsThe daybeacon symbols are shown in Sec-

tion Q (80 through 83) of Chart No. 1. The cen-ter of the daybeacon symbol is located at itsgeographic position. Daybeacons alongdredged channels are also charted in theirtrue positions, unless they are on oppositesides of a channel and plot less than 0.5 mm

13Note that these are depicted in upright letters, rather than italics, because these are fixed structures.

apart. In this case, to add clarity, the aids maybe separated to 0.5 mm. However, daybeaconsare not moved off ranges (see below) nor natu-ral objects.

There are two principal standard symbolsused to depict daybeacons; a triangle and asquare. Triangular daybeacons (starboardhand red marks with even numbers in theIALA-B system) are typically represented byan equilateral triangle 2.0 mm on each side.(To avoid chart clutter in congested areas, a1.5 mm triangle may be substituted.) Red tri-angular daybeacons are shown with a magentafill, those with other colors (e.g., preferredchannel daybeacons) are unfilled and the col-ors and identifying numbers or letters are in-cluded in the label.

Square daybeacons (port hand marks withodd numbers in the IALA-B system) are typi-cally represented by a square 1.65 mm on eachside (or a smaller 1.3 mm square). The squaresymbol is also used to represent rectangular,round, octagonal or diamond-shapeddaybeacons). Green daybeacons are shownwith a green fill, those with other colors (e.g.,preferred channel, safe water, or special pur-pose daybeacons) are left unfilled, and the col-ors and identifying numbers or letters are in-cluded in the label.

Figure 5�7 shows daybeacons in the vicin-ity of Hereford Inlet, New Jersey.

�Daybeacon LabelsLabels include the color(s) of the daybeacon

and the identifying numbers and letter(s),charted in black vertical type.13 Color choicesinclude red (starboard hand markers), desig-nated with an �R,� red and green (junction bea-cons with preferred channel to port), desig-nated with an �RG,� red and white (fairwaybeacons), designated with an �RW,� green(port hand markers), designated with a �G,�


pict daybeacons which do not have identify-ing numbers or letters.

Daybeacons that have information writtenon the dayboards may have that information(e.g., �Rock�) charted as an optional part of theaid characteristic. Pr ivate daybeacons arelabeled �Priv.�

green and red (junction beacons with preferredchannel to starboard), designated with a �GR,�yellow (quarantine area, practice area), desig-nated with a �Y,� and white (regulatory warn-ing, state boundary), designated with a �W.�

Numbers and letters are charted as appro-priate. The abbreviation �Bn� is used to de-

Fig. 5-7. Excerpt from NOS Chart No. 12316 (Little Egg Harbor to Cape May, New Jersey). Notethat the buoys in Hereford Inlet are not charted. Note also the daymark symbols

marking the Great Flat Thoro. Cupolas and a standpipe can be seen as landmarks.Lights, lighted, and unlighted buoys are also shown.


Ranges (M)According to the Light List, ranges�

�are non-lateral aids to navigation sys-tems employing dual beacons which,when the structures appear to be inline, assist the mariner in maintaininga safe course. The appropriate nauti-cal chart must be consulted when us-ing ranges to determine whether therange marks the centerline of the navi-gation channel and also what sectionof the range may be safely traversed.Ranges display rectangular dayboardsof various colors and are generally, butnot always lighted. When lighted,ranges may display lights of any color.�

As constructed, a range consists of twobeacons, one is called the front range markerand is lower in height than the other, calledthe rear range marker. The rear marker isusually located some distance from the frontmarker. (Often the front range marker is ona fixed structure in the water, and the rearrange marker is on land.) When these twomarkers appear directly in line (one behindthe other, but both visible because the rearmarker is higher) they are said to be �inrange,� or �in transit� in British usage. Theline defined by the range is called a �rangeline� or �leading line.� Daybeacons and othercharted objects forming a range are oftencalled �leading marks.� Likewise rangelights are sometimes termed �leadinglights.�

Approaching the front range marker, if thetwo marks are exactly in range, the vessel�sposition is exactly along the range line. If thelower marker is to the left (right), the vesselmust alter course to the left (right) to rejointhe range. Because of geometric consider-ations, the horizontal angle between the rangemarkers seen by a vessel a fixed distance awayfrom the channel centerline increases withdecreasing distance (Brogden). Thus, the sen-sitivity of the angle to side-to-side excursions

increases as the vessel draws closer to themarkers. The range markers provide an accu-rate and easily obtained line of position. Arti-ficial ranges (lighted or unlighted) have beeninstalled in line with channels in many ports.In cases, such as the Delaware River, wherethe river has many bends, separate rangesmark each of the straight sections, and navi-gation amounts to following a sequence ofranges throughout the voyage. Most rangesare aligned with the center of the channel, butin some areas more than one range is used todefine the inbound and outbound ranges of thechannel.

Range lights may be of any standard lightcolor or period, the principal requirement be-ing that these stand out from their surround-ings. Thus, for example, green rather than redor white lights might be used to mark a rangethat would be aligned with the setting sun.Most range lights show a high intensity beamwithin only a very narrow arc of visibilitymarking the channel centerline and are ob-scured around the remainder of the horizon.These lights appear to lose brilliance rapidlyas the vessel strays from the range line. Rangelights are often visible at distances consider-ably greater than the actual usable range, toensure that they can be seen in adverseweather conditions.

After extensive research and testing, theUSCG is preparing to install �light pipes�on many channel ranges around the country(Professional Mariner, 1994). These lightpipes are fiberglass tubes, approximately 15feet long and 6 inches in diameter with aspecial film on the inside and a light sourceat one end. The light pipe is placed directlyin front of the boards of the range markers.The light pipes are highly conspicuous atranges up to several miles, and�comparedto conventional lights�it is much easier todetect the alignment (or misalignment) oftwo vertical lines of light. Light pipes willbe supplied with various colors and charac-teristics in the same manner as conventionalrange lights.


�Charting PracticesOnly ranges published in the Light List are

charted. As with other ATONs charting con-ventions consist of a symbol and associatedlabels.

Range lights are separately charted asnoted above in the section on lights. If the scaleis too small to chart a pair of range lights in-dividually, these are shown with one light dotand labeled, for example, �2F.� A passing light,if installed, is generally placed on the frontlight of a range structure located in the wa-ter. The passing light serves as an extra pre-caution to alert mariners to the existence ofthe range light structure when approachingthe light from its dark side at night. (Not allranges are equipped with passing lights, how-ever.) Because the passing light is of second-ary importance to the range light, its charac-teristic is charted on a separate line below therange light label�in the same order as shownin the Light List. If the visibility of the pass-ing light is included in the Light List, it is alsoincluded in the chart label.

�Symbol (M 1)The range symbol is shown in Section M 1

of Chart No. 1. The usable portion of ranges isshown by a solid line to the point where thevessel should leave the range. (Defining thelimits of the range is obviously of key impor-tance for curving channels.)

From the point where the range should beleft, the range is continued with a short-dashedline to the rear navigational aid.

In the event of extreme shoaling or shoal-ing over a large area in an improved channel,range lines may be dashed, or even omitted,through a shoaling area that is depicted by hy-drography.

Figure 5�8 shows ranges used to mark asection of the upper Delaware River, as shownon NOS Chart 12314 (Delaware River, Phila-delphia, PA, to Trenton, NJ).

�Range LabelsThe range label shows the name of the range

and the bearing of the range (in degrees truealong the range in the direction of the frontmarker) if these are published in the Light Listand considered useful to the mariner.

�Dredging RangesThe USACE has established ranges in some

areas to control channel maintenance dredg-ing. These ranges (often unlighted) are not in-tended for navigation and are charted only asa �DREDGING RANGE.� Structures compris-ing this range are charted as landmarks (seeChapter 6). If the dredging structure is listedin the Light List, the structure label provideslight and fog signal information.

�Natural RangesSpires, cupolas, towers, tanks, and other

artificial or natural features may form �natu-ral ranges� which chart users sometimes rec-ommend for charting. These natural rangesare not charted unless recommended by theUSCG and published in the LNM.

Radiobeacons and Related Aids (S)A brief introduction to radiobeacons pro-

vided in the Light List states,

�As the first electronic navigation sys-tem of navigation, radiobeacons pro-vided offshore coverage and also be-came the first all-weather electronicaid to navigation. The Coast Guard op-erates about 200 radiobeacons locatedon the Atlantic, Gulf, and Pacificcoasts, and on the Great Lakes. Theseradiobeacons are located at light-houses, on large buoys and along thecoasts. All positions are charted.

�In order to use this system, the mari-ner needs a radio direction finder,which is a specifically designed radioreceiver with a directional antenna.This antenna is used to determine thedirection of the signal being emitted bythe shore station, relative to the ves-sel .

�The basic value of the radiobeacon sys-tem lies in its simplicity of operation andits relatively low user costs, even thoughthe results obtained may be somewhatlimited. The general problems and prac-tices of navigation when using


radiobeacons are very similar to thoseencountered when using visual bearingsof lighthouses or other charted objects.

�A radiobeacon is basically a shortrange navigational aid, with rangesfrom 10 to 175 nautical miles. Althoughbearings can be obtained at greaterranges, they will be of doubtful accu-racy and should be used with caution.When the distance to a radiobeacon is

greater than 50 miles, a correction isusually applied to the bearing beforeplotting on a Mercator chart. These cor-rections, as well as information on ac-curacy of bearings, plotting, and othermatters are contained in�Radio Navi-gation Aids�[or the U.S. Coast Pilot].�

An individual radiobeacon can be used todetermine a single LOP and for tracking orhoming purposes. If the vessel makes a 90°�dog leg� of known length, the approximate

Fig. 5-8. Excerpt from NOS Chart No. 12314 (Delaware River, Philadelphia, PA,to Trenton, NJ). Three ranges are shown on this inset. The rear range markerfor the Kinkora Range is an occulting white light with a 4-second period. The

front range marker for this same range is a quick-flashing white. The boundarybetween the Roebling Range and the Kinkora Range is close to the unlighted

red nun �70.� Green buoy �71� is a lighted quick-flashing buoy. The reason thatthe quick characteristic is used is that two course changes are necessary over a

short distance. Landmarks shown include tanks and a spire.


distance off (Maxim) a single radiobeacon canbe calculated from the length of the dog legand the degrees of bearing change.Radiobeacons are typically located at or near-harbor entrances to maximize the utility of thehoming or tracking capability of the system.The LOP from a radiobeacon can be crossedwith another LOP (e.g., from a nearbyradiobeacon or visual aid) to determine a fix.Mariners using radiobeacons for tracking orhoming purposes are cautioned to keep trackof the vessel�s position so as to avoid runningaground or into hazardous waters. Historicalexamples (see Maxim) of homing without dis-tance checks abound. Additional material onradiobeacons can be found in the referenceslisted at the end of this chapter (e.g., Bowditch,Dutton, Hobbs).

For many years, this system, also called ra-dio direction finder (RDF), had the largest num-ber of users of any radionavigation system. Inrecent years, LORAN-C and GPS have becomesystems of choice for marine navigation. How-ever, many radiobeacons are being modifiedto broadcast differential GPS corrections, soradiobeacons will continue in service for sometime to come.

Marine radiobeacons operate in the 200 to400 kilohertz region, just beneath the AMbroadcast band. These radiobeacons transmita Morse code identifier for 50 seconds, fol-lowed by a 10-second continuous tone at theend of each operating minute:

The function of the Morse code se-quence is to provide positive iden-tification of the radiobeacon. Posi-tive identification of radiobeaconsis as important as positive identifi-cation of any ATON. Morse codeidentifiers are often (but not al-ways) an abbreviation of the facil-ity name. Thus, for example, the twoletter Morse code identifier forCape May is �CM,� and that forBarnegat Inlet is �BI.� However,there are exceptions (Cape Henry,for example, carries the identifier�CB�), so it is necessary to consultthe Light List for authoritative in-

formation. The Light List providesthe Morse symbols (e.g., Cape Mayis �.�. � �) so it is not necessary toknow Morse code to use the system.

The function of the continuous toneis to provide the best signal for de-termining an �aural null� in rotat-ing the antenna to determine thebearing to the station.

�Charting PracticesAll marine radiobeacons transmitting sig-

nals in areas where hydrography and othernavigational information is provided arecharted. The useful range of the radiobeacon,along with other pertinent information forradiobeacons in U.S. waters is provided in theLight List. On charts of scale 1:500,000 andsmaller, radiobeacons are not shown if thechart does not permit navigation within theirrange. (Low power radiobeacons with a use-ful range of 10 miles or less are normally omit-ted from small-scale charts where larger scalecharts are available.)

This section provides information on chart-ing practices for radiobeacons and related in-formation. Charting conventions consist of aradiobeacon symbol and associated label(s).

�Symbol (S 1)Most radiobeacons are collocated with an-

other visual aid to navigation. If so, the chartsymbol will include that for the co-located aid,together with a radiobeacon symbol (see Sec-tion S 1 of Chart No. 1) consisting of a 7.1 mmdiameter magenta circle centered on the po-sition of the aid. For stand-alone radiobeacons,the black �position accurate� landmark sym-bol (see Chapter 6) is placed at the center ofthe magenta circle.

�LabelsIn addition to providing information about

the �host aid� (e.g., buoy, light, etc.), if one ex-ists, the label provides information about theradiobeacon. The label is given in black verti-cal type if the antenna is attached to a fixedaid, and italic type if the antenna is attachedto a floating aid.


The label includes the abbreviation �R Bn,�the frequency (in kilohertz), and the Morsecode characteristics, regardless of the chartscale.

�Aeronautical RadiobeaconsAeronautical radiobeacons (which operate

on similar frequencies to marine radiobeaconsand can be received by the same equipment)are sometimes useful for marine navigation,particularly if located in close proximity to thecoastline or if there is no rough terrain be-tween the beacons and the coastline thatmight distort signal propagation.

If charted, the aeronautical radiobeacon isdepicted with a black �position accurate� land-mark symbol and a 7.1 mm diameter magentacircle centered on the landmark symbol. A la-bel in conventional black type is placed adja-cent to the symbol and clear of the magentacircle. The label includes the abbreviation�AERO R Bn� and the frequency and charac-teristics of the radiobeacon.

Miscellaneous Related InformationNautical charts also include information on

courses, recommended and alternate courses,routing systems, traffic schemes, and areas andlimits. These are discussed in Chapter 7. Trialcourses, however are included in this chapter.

�Measured Course (Q 122)A trial course is a course at sea, the ends

of which are marked by ranges ashore and thelength of which has been accurately measured.Trial courses are used by vessels to calibratelogs and other instruments that measurespeed, as well as to prepare graphs or tablesof engine revolutions per minute (RPM) ver-sus speed through the water. (See Maxim orother references for details.)

A standard symbol (see the excerpt notedin Section Q 122 from Chart No. 1 and repro-duced here in figure 5�9) is used to mark therange or measured course ashore. The courseand length of the trial course are indicated bya label.

Fig. 5-9. Trial course symbols shown on Chart No. 1.


U.S. Coast Guard Buoy Tender passing by green-lighted radar-reflective buoy.Angle of buoy suggests current is moving from right to left in this photograph.

Approximately 4,600 lighted buoys mark U.S. waters.Official U.S. Coast Guard photograph.

to the mariner. Because the cost of establish-ment and periodic maintenance are sufficientlyhigh, ATONs are not casually placed. So it iscertain that if an ATON has been put in a givenplace, it is because this location has real sig-nificance to the mariner. Therefore, it is par-ticularly important that the mariner be famil-iar with the uses, significance, and chart con-ventions employed to depict this aid.

Concluding RemarksAs noted, this chapter is long and quite de-

tailed. Nonetheless, the information pre-sented is very important, and bears reading(preferably with a nautical chart and Chart No.1 readily at hand) and rereading to ensurecomplete familiarity with this important topic.

Unlike many of the other objects or featuresdepicted on the chart, ATONs are deliberatelyplaced so as to optimize information provided

� � � � � � � � � � � � � � � � � � � � � � � � ��The consequences [of poor cartography] could

be dire. During the Napoleonic Wars, British lossesby shipwreck, caused by bad charts as well as badweather, were eight times as great as those inflictedby the enemy.

Wilford

� � � � � � � � � � � � � � � � � � � � � � � � �


References

Anon. �Charthouse Chatter,� ProfessionalMariner, Issue No. 3, October/November,1993, p. 7.

Anon. �Charthouse Chatter,� ProfessionalMariner, Issue No. 4, December/Jarnuary1994, pp. 6�7.

Brogden, W., �Inside Ranges A Look at WhatMakes These NAVAIDS so Useful,� OceanNavigator, Issue No. 60, March/April 1994,pp. 74, et seq.

Burch, D., Emergency Navigation, Interna-tional Marine Publishing Company,Camden, ME, 1986.


Caldwell, B., Lighthouses of Maine, GannettBooks, Portland, ME, 1986.

Dahl, N., The Yacht Navigator�s Handbook,Hearst Books, New York, NY, 1983.

National Imagery and Mapping Agency. Ameri-can Practical Navigator, An Epitome of Navi-gation (Bowditch), Publication No. 9, NIMAStock No. NV PUB 9 V1, Bethesda, MD,1984.

National Imagery and Mapping Agency.Radionavigation Aids, RAPUB 117,Bethesda, MD, (Annual).

de Gast, R., The Lighthouses of the Chesapeake,The Johns Hopkins University Press, Bal-timore, MD, 1993.

Dutton�s Navigation and Piloting, FourteenthEdition, Naval Institute Press, Annapolis,MD, 1985.

Eyges, L., The Practical Pilot, Coastal Naviga-tion by Eye, Intuition, and Common Sense,International Marine Publishing, Camden,ME, 1989.

Hobbs, R. R., Marine Navigation Piloting andCelestial and Electronic Navigation, ThirdEdition, Naval Institute Press, Annapolis,MD, 1990.

Holland, F. R., Jr., America�s Lighthouses AnIllustrated History, Dover Publications,New York, NY, 1981.

Human Technology, Inc. Desk Reference Guide:Specifications Unit, Chart and Map, Fea-ture: Buoy. Report developed for NationalOcean Service, Charting and Geodetic Ser-vices, Marine Chart Branch, Under Con-tract OPM-85-77, McLean, VA, October1985.��: Daybeacon.��: Light.��: Marker.��: Obscured Sector.��: Range Line.��: Riprap.

Ihnat, D. J., CDR, U.S. Coast Guard. �QuarterlyReport of Short Range Aids to Navigation,�Commandant (G-NSR-1), quarter ending 31March 1993. Data updated to January 1994with personal communication, Lt. MikePeterson, USCG.

Maloney, E. S., Chapman Piloting, 60th Edition,Hearst Marine Books, New York, NY, 1991.

Maxim, L. D., Advanced Coastal Navigation,Second Edition, United States CoastGuard Auxiliary, Coast Guard AuxiliaryNational Board, Inc., Washington, DC,1990.

Mellor, J., The Art of Pilotage, Sheridan House,Dobbs Ferry, NY, 1990.

Milligan, J. E., The Amateur Pilot, Cornell Mari-time Press, Centreville, MD, 1982.


Moody, A. B., Navigation Afloat, Van NostrandReinhold, New York, NY, 1980.

Naish, J., Seamarks, Their History and Devel-opment, Stanford Maritime, London, UK,1985.


Schlereth, H., Commonsense Coastal Navi-gation, W. W. Norton Co., New York, NY,1982.

U.S. Department of Commerce, NationalOceanic and Atmospheric Administra-tion, National Ocean Service, and De-partment of Defense, National Imageryand Mapping Agency. Chart No. 1 UnitedStates of America Nautical Chart Sym-bols Abbreviations and Terms, Ninth Edi-tion, Washington, DC, January 1990.

U.S. Department of Commerce, Coast andGeodetic Survey, Nautical ChartManual, Volume One: Policies and Pro-cedures , Seventh Edition, Washington,DC, 1992

U.S. Department of Transportation. UnitedStates Coast Guard Aids to Navigation,

COMDTPUB P16502.8, Washington, DC,May 1988.

U.S. Department of Transportation. UnitedStates Coast Guard, Light List, Volume1, Atlantic Coast, St. Croix River, Maineto Toms River, New Jersey, COMDTPUBP16502.1, Washington, DC, 1991.

U.S. Department of Transportation. UnitedStates Coast Guard, LORAN-C UserHandbook, COMDTPUB P16562.6, Wash-ington, DC, 1992.

Walsh, G., �Chartroom Chatter,� OceanNavigator, Issue No. 60, March/Apri l1994, p. 14.

Wilford, J.N., The Mapmakers: The story ofthe great pioneers in cartography from an-tiquity to the space age, Vintage Books,New York, NY 1982.

Landmarks 6-1

brief list, landmarks are artificial features.But landmarks also include prominent natu-ral features such as a mountain peak, glacier,volcano, cliffs, or other suitable natural ob-jects.1

This chapter provides information on thetype and utility of landmarks and how theseare depicted on nautical charts. This chapteralso identifies sources of additional informa-tion (e.g., the U.S. Coast Pilot, Chart No. 1,United States of America Nautical Chart Ab-breviations and Terms and the Light List) ,which supplement that provided on the nau-tical chart. Finally, the chapter concludeswith practical pointers on the selection of land-marks for navigation and why landmarks aresometimes not seen or identified when under-way.

Importance of Landmarks in CoastalNavigation

All mariners, with varying degrees of for-mality, employ landmarks for navigation.Used in conjunction with �seaman�s eye� orinformal navigation, landmarks serve to de-termine an approximate position, define haz-ardous areas, provide directions for harbor

1It is important that natural features have clearly defined reference points that can be accuratelylocated if these are to be charted as landmarks. Mountains with rounded peaks would probably not becharted as landmarks, although the topography would be shown.

CHAPTER 6

Landmarks

Introduction and OverviewAccording to accepted NOAA Nautical

Chart Manual nomenclature, a landmark�

�...is any fixed natural or artificial ob-ject on land which is prominent fromseaward and can be used in determin-ing a direction or position. The termexcludes objects expressly erected fornavigational purposes such as lights ordaybeacons. Prominence is the firstrequisite for a landmark, but ease ofpositive identification is also impor-tant. The unusual or unique featuremay qualify as a landmark because it iseasy to identify although not particu-larly prominent.�

A more complete list of landmarks typicallycharted is provided later in this chapter.Briefly, however, landmarks include such ob-jects as buildings, stacks, tanks, domes, tow-ers of various descriptions, spires and radioantennas. (Not all of these objects in a givenarea would be charted as landmarks, however.)Often, as in the examples presented in this

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�Even with the best charts, we are cautiousabout fixing our position, for it is so easy to goof.And the easiest way of all is by taking a mark,assuming it is the right one, and ignoring anyothers that may be in sight.�

Patrick Ellam

○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○


entry, etc. For example, directions to a favor-ite anchorage based on recent local knowledgemight be given as:

�Stay in the main river channel untilpassing the red brick pump house onthe left (when northbound) then altercourse to starboard until the bow isaligned with the blue A-frame buildingbetween the flagpole and the marinaand the stern with the pump house.Continue along an imaginary line join-ing these two landmarks until well pastthe small island on the right-hand side,then turn to port�.�

More formally, landmarks are charted ob-jects used for determining LOP (e.g., with ahand-bearing compass or radar)2 and circlesof position (e.g., with radar or an optical rangefinder for landmarks with charted height in-formation) so as to determine a fix or estimatedposition for the vessel. Table 6�1 providesboth general and specific illustrations of howinformation derived from landmarks can beused for marine navigation. As with ATONs,discussed in Chapter 5, landmarks can be usedto fix the vessel�s position, to serve as the vi-sual equivalent of radio beacons for homingor tracking purposes, to evaluate whether ornot a vessel is in dangerous waters (e.g., byuse of a danger bearing or danger circle), toidentify turn points, and for a variety of spe-cialized purposes such as compass calibrationor to determine whether or not the vessel�sanchor is dragging. Included in the list of ref-erences at the end of this chapter are textsthat discuss these topics in detail. Names en-closed in parentheses (e. g., Bowditch) denoteparticularly pertinent references.

In short, charted landmarks are the logi-cal equivalent of shore-based ATONs for use

2Landmarks are generally selected so as to be detectable and identifiable from the sea by visual means.Some may be detectable and identifiable by radar, but charting as a landmark offers no guarantee that theobject can be detected and identified by radar. In particular, landmarks in built-up areas, such as cities, areoften �lost� among many land returns.

GENERAL:

� Used for determining range or bearing byvisual means (or radar) in coastal watersso as to determine a fix or estimatedposition;

SPECIFIC ILLUSTRATIONS:

� Used for determination of fix, running fix,estimated position, set and drift of cur-rent;

� Used for plotting danger bearings, dangercircles, horizontal danger angles;

� Used (in conjunction with danger bearingor circle) for evaluation of vessel's posi-tion with respect to unobservable hazardsto navigation;

� Used for establishing vessel turningbearings;

� Used as visual equivalent of RDF beaconfor homing or tracking purposes;

� Used for compass calibration; and

� Used for determining whether or not ananchor is dragging.a

a The landmark need not be charted for this purpose.

in coastal waters. If accurately charted (morebelow), detectable, and readily identifiable,these can be superior to the use of floatingATONs (buoys)�recall that fixed structuresare preferable to floating structures for posi-tion determination. In some areas of highpopulation density or numerous conspicuousnatural features, charted landmarks are ac-tually more numerous than charted ATONs.

Table 6-1. Utility of Landmarks Shownon Nautical Chart

Landmarks 6-3

Types of LandmarkTable 6�2 provides a list of the more com-

mon artificial landmarks depicted on nauti-cal charts, together with pertinent brief re-marks. Refer to the Glossary given in appen-dix A for more complete definitions. It isworthwhile to study these and to gain practi-cal familiarity with landmarks by systemati-

cally comparing the chart representation oflandmarks in your area with the physical ap-pearance of the object. These �training ses-sions� can be made an enjoyable part of eachcruise. An experienced navigator can oftenform a highly accurate mental picture oflandmarks to be found in unfamiliar wa-ters merely by studying the chart.


A N T E N N A Usually reserved for those re-flecting antennas which arelarge in size and of open or grid-type construction.

BUILDING See HOUSE.

CHIMNEY A relatively small, upright struc-ture projecting above a buildingfor the conveyance of smoke.

CUPOLA A turret or small dome-shapedtower which rises from a build-ing and is small compared to thebuilding.

DOME A large, hemispherical cupola,or a roof that is rounded or manysided. Their appearance lookslike a large �golf ball.�

DOME (RADAR) A dome known to contain radartype of equipment shall becharted as DOME (RADAR). Ifthe radar use is not known, sim-ply chart as DOME. Their ap-pearance looks like a large�golf ball.�

FLAGPOLE A single staff flagpole rising fromthe ground and not attached toa building.

F L A G S T A F F A flagpole rising from a buildingis not necessarily the mostprominent part of a building forlandmark recognition purposes.

FLAG TOWER Any scaffoldlike tower on whichflags are hoisted, such as aCoast Guard Skeleton steel flag-pole.

GAS TANK Since a gas or oil tank differs inshape and size from a watertank, the compound name is

or OIL TANK used. These are usually cylin-drical.

Table 6-2. Illustrative Landmarks


Table 6-2. Illustrative Landmarks (continued)


OIL TANK See GAS TANK.

RADIO MASTRADIO TOWER Radio towers and radio masts

are metal structures used to el-evate antennas. A RADIOTOWER is a tall structure usu-ally of open lattice-type con-struction and always self-sup-porting. A RADIO MAST is avery tall slim structure held verti-cal by guylines.

RADIO TOWERKAGT1340 kHz

RADIO MAST 1015 FT(TV, FM)(STROBE, R LTS)

RADIO TOWER 215 ft(MICROWAVE) orMICRO TOWER

H O U S E Charted when the building itselfor BUILDING is the landmark.

LOOKOUTT O W E R Any tower, usually of open con-

struction, surmounted by a smallhouse in which a watch is habitu-ally kept, such as a Coast GuardLookout Tower or a Fire Look-out Tower.

LORAN-CS T A T I O N S (See: Appendix A. Glossary.)

MICRO TR A tower which contains micro-wave transmitters and receivers,used in the transmission of com-munication signals.

MONUMENT A structure, such as a buildingor sculpture, erected as a me-morial. Also used to denote aboundary marker for surveyingor other purposes. There is nostandard size or shape to amonument. Some, such as theWashington Monument, re-semble an obelisk (i.e., a four-sided shaft that tapers to a pyra-midal point), others assume avariety of shapes.

Landmarks 6-5

Table 6-2. Illustrative Landmarks (continued)

TOWER; TR That part of a structure higherthan the rest, but having verticalsides for the greater part of theheight.

Any enclosed structure, whetheror not its sides are vertical, withbase on the ground and high inproportion to its base.

T R E E �Lone tree� or �conspicuoustree,� are not used since the ad-jective is assumed. Otherwisethe tree would not serve as alandmark.

WATER TOWER A decorative structure enclosinga tank or standpipe. Its appear-ance may prevent its being rec-ognized as a water tank orstandpipe.

WINDMILL A self-explanatory term.

S P I R E A slender point structure sur-mounting a building. It is rarelybroken by stages or other fea-tures. The term SPIRE is not ap-plicable to a short pyramid-shaped structure rising from atower or belfry. Spires are oftenseen atop churches.

S T A C K This term is applied to any tallsmokestack or chimney, regard-less of color, shape, or materialwhen the stack is more promi-nent as a landmark than anybuilding in connection with it.

S T A N D P I P E ; A tall cylindrical structure in a wa-terworks system, the height ofwhich is several times greaterthan the diameter.

T A N K A water tank elevated highabove the ground by a tall skel-eton framework or support. The

word �elevated� is omittedsince a tank would not bea landmark unless el-evated.

OTHER EXAMPLES OF LANDMARKS NOT ILLUSTRATED ABOVETHAT MAY BE USED ON CHARTS:

Battery, Blockhouse, Buddhist Temple, Camping Site,Capitol, Castle, Cemetery, Chapel, Church, ChurchTower, Church Spire, Church Cupola, Company, Court-house, Cross, Elevator, Factory, Flare Stack, Fort,Fortified Structure, Gable, Government House, High

School, Hotel, Institute, Josshouse, Magazine,Marabout, Minaret, Mine, Mosque, Pagoda, Pavilion,Quarry, School, Shinto Shrine, Silo, Small Fort, Tele-graph, Telephone, Temple, Tomb, University, Well,Windmotor.

S’PIPE

Sources: Desk Reference Guide, Bowditch, Chart No. 1.


For most landmarks (e.g., buildings,churches, radio towers), object definitions arefamiliar and the mariner should have little orno difficulty correlating the chart represen-tation with the physical appearance of the ob-ject. In some cases (e.g., cupola, dome, chim-ney, stack), the definitions are more subtleand/or the objects may be less familiar so morestudy and on-the-water comparisons are ap-propriate.

Objects Not Normally Depicted As Land-marks

There are also several classes of objectsthat are not typically selected as landmarkson nautical charts. (These objects may beshown on certain charts in areas where suit-able landmarks are few and far between.)Table 6�3 provides a list of those either inten-tionally or unintentionally omitted. In themain, the reasons for not selecting these ob-jects as landmarks are obvious. For example,objects of a temporary nature, such as a con-struction crane, would be a poor choice for alandmark since the object would probably bemoved to another location by the time that thechart was printed.

Trees are another example of an object notnormally charted as a landmark. Think of theconsequences, for example, if the tree werestruck by lightning or chopped down. Evenworse, suppose there were another tree stand-ing one-half mile away!

The charting of movable objects as land-marks is generally avoided. A gantry crane ata shipyard may be a very prominent feature,but it would not have a fixed geographic posi-tion and, therefore, would have little utilityfor precise fixing of a vessel�s position.

Signs are not typically charted as land-marks. However, an unusually conspicuoussign, especially in an area without other suit-able landmarks, may be charted. The eleva-tion and lighting of the sign are considered inmaking the determination of whether or notto select the sign as a landmark. Signboardsdisplaying navigational information may beconsidered as landmarks if they displaynavigationally relevant information, for ex-ample, signboards used to mark distances

INTENTIONALLY NOT SELECTED:

� Objects of a temporary nature (e.g., vertical

construction crane, exploratory oil-drilling rig,

dredge);

� Inconspicuous objects, unless specifically

requested by a competent authoritative source

(e.g., survey tower or target, object used by the

USCG in buoy placement);

� Objects which move in position;

� Classified military objects for which no release

by competent authority can be obtained;

� Signs, unless unusually tall, large, or otherwise

conspicuous or in an area devoid of other

objects of landmark value;

� Multiple objects of the same type very close

together or in a relatively small area (in this

case only the tallest or largest items, and/or

those on the outer limits of the complex will be

charted);

� Trees unless (in exceptional circumstances) no

other visual references are available to the

mariner; or

� Omni stations, unless recommended by a

reliable source.

UNINTENTIONALLY OMITTED:

� Objects missed in a previous survey or those

which have been constructed since the last

survey.

Table 6-3. Items Generally Not Charted asLandmarks on the Nautical Chart

along a waterway. As another example, signsproviding water-level information are nor-mally charted even if not visible from a dis-tance.

It may come as a surprise to some readersthat not all items potentially suitable as land-marks are actually charted. To be sure, insparsely populated flat land areas, nearly allsuitable landmarks would be charted. But inbuilt-up areas, only a few otherwise suitable

Landmarks 6-7

objects would be plotted as landmarks.3 Forexample, large cities, such as Boston, NewYork, and Philadelphia, have literally thou-sands of buildings that might be suitable land-marks. However, in practice only a handful�those believed sufficient for safe and efficientnavigation�are actually depicted as land-marks on the chart. Figure 6�1 provides suchan illustration for the Philadelphia, PA�Camden, NJ, area. Indeed, one of the criteriafor charting landmarks in the Desk ReferenceGuide, is that �consideration should be givento the number and quality of other chartedlandmarks or reported objects of landmarkvalue in the area.� Therefore, the marinershould not expect that the nautical chart willdepict all possible structures as landmarks.Generally, this poses no particular problemto the informed mariner. But while underwaythis can sometimes lead to confusion and iden-tification problems. For example, several wa-ter tanks may be visible in an area in whichonly one or two are charted. In this case, themariner might be faced with the problem of�which of the tanks in view are those charted?�

How Landmarks Are Depicted on theChart

Landmarks are charted in the exact posi-tion reported on source documents. Both asymbol and one or more labels usually accom-pany a charted landmark.

�SymbolsIn certain cases, the outline shape of a

prominent structure may be charted to scaleif it is relatively large or of particular inter-est and of landmark value (e.g., the Pentagon,Fort McHenry). More typically, however, land-marks are charted with standard symbols.Landmark symbols are shown in Section E ofChart No. 1. According to the accuracy with

which the landmark�s location is known, thesymbols include:

� An accurate landmark symbol, consist-ing of a black circle 1.18 mm (0.047") inradius with a center dot 0.25 mm(0.010") in diameter in cases where theposition of the landmark is consideredto be located within 10 feet of its cor-rect geographic location.

� An approximate landmark symbol, con-sisting of a smaller black circle 0.5 mm(0.020") in radius without any centerdot in cases where the landmark is lessaccurately located than above, but gen-erally considered to be within 100 feetof its correct geographic location.

� An approximate landmark symbol ex-plained above, but with the letters �PA�(position approximate) as part of the la-bel in cases where the location of theobject is considered to be within 101 to300 feet of its correct geographic loca-tion. Such landmarks, sometimes re-ferred to as inexact position landmarks,are only charted if they serve a �criti-cal� navigation need.

In some cases a landmark, such as a build-ing, will be drawn to scale and, additionally,have some contained feature depicted with theaccurate or approximate position label. For ex-ample, the Customs House in Philadelphia,shown in figure 6�1 is drawn to scale. Addi-tionally, the tower atop this building is shownas a landmark with the accurate position sym-bol. Identifying particular portions of struc-tures as landmarks makes it possible to takeaccurate bearings.

Excepting those landmarks which aredrawn to scale, charted landmarks are shown

3Aside from the logistics and compilation problems of charting all possible landmarks, the resultantchart (with requisite labels) would be physically impossible to produce. Moreover, NOAA is actively seek-ing ways to reduce chart �clutter� and make more �user-friendly� products.


Fig. 6-1. Excerpt from NOSChart No. 12313 (Philadelphiaand Camden waterfront). Of thethousands of buildings in thePhiladelphia, PA-Camden, NJ,area, only a few are chartedas landmarks. This inset fromChart 12313 illustrates stacks,spires, tanks, and towers aslandmarks. The Camden CityHall Tower is a primary label.Less well-known, the CustomsHouse in Philadelphia is writ-ten TOWER (CUSTOM HO).Three hospitals and a fireboatstation are shown in this chartextract. These are not chartedfor their landmark value, butrather for their functional value.

Landmarks 6-9

in only one of two sizes (1.18 mm radius circleand 0.5 mm radius circle) regardless of actualdimensions. In this sense, all landmarks arealike. Something more is clearly needed tohelp the navigator identify the landmark. Thisadditional information is provided in labelsthat are printed next to the landmark symbol.

�LabelsAccompanying the landmark symbol is one

or more labels. Labels are used to provide ad-ditional information useful in identifying thelandmark. The label also provides a redun-dant indication of the accuracy with which alandmark is located.

The first label depicts the primary natureor descriptive term most likely to identify theobject (e.g., TOWER, STACK, CHIMNEY) setin 6 pt. Newton Medium type and placed inclose proximity to the landmark symbol.Landmarks charted with the accurate land-mark symbol are labeled entirely in verticalcapital letters, those charted with the approxi-mate landmark symbol are labeled with initialcapitals only. Thus, for example, a tower con-sidered to be located within 10 feet of its cor-rect position would include the accurate land-mark symbol and the label �TOWER,� whereasone located to within 100 feet of its true loca-tion would have the approximate landmarksymbol and the label �Tower.�4 A tower witha location uncertainty greater than 100 feetwould carry the label �Tower PA.� A partiallist of standardized labels and authorized ab-breviations are shown in table 6�4.

Secondary and descriptive labels may beadded for clarity and are enclosed in paren-theses to the side or underneath the primarylabel. The capitalization convention for thesecondary label(s) is the same as that for theprimary label. Consider a lighthouse, for ex-ample. If operational, this would not be con-sidered a landmark�rather it would be in-cluded as an ATON (see Chapter 5). However,

Table 6-4. Labels and Authorized Abbreviations

ANTENNA (ROUND, PARABOLIC, ORRECTANGULAR)

CHIMNEY (CHY)CUPOLA (CUP)DOME (a dome known to contain radar equip-

ment shall be labeled DOME (RADAR)FLAGPOLE (FP)FLAGSTAFF (FS)FLAGTOWER (F TR)GAS TANK or OIL TANKHOUSE or BUILDING (HO or BLDG) (if the

structure encloses equipment of naviga-tional use, a one-word description shallfollow the primary level (e.g., BUILDING(VOR))

LOOKOUT TOWER (LOOK TR)LORAN STATIONSMICRO TRMONUMENT (MON)RADIO MAST (R MAST) followed by, if known,

radio frequency, height, call letters. Also(TV, FM, AM, STROBE, or RLTS).

RADIO TOWERSP IRESTANDPIPE (S'PIPE)TANKTOWER (TR)T R E EWATER TOWERWINDMILL

if no longer used as a lighthouse, it would beclassed as a �tower.� But, because the term�tower� includes many different types of struc-tures, it is desirable to add a secondary ordescriptive label, �abandoned lighthouse,� tosupplement the primary label. Accordingly,such a landmark (if accurately located) wouldbe labeled TOWER (ABAND LT HO).

Names of certain locally well-known build-ings may be shown as secondary labels to fa-cilitate identification. For example, DOME

4The lone exception to this rule is the case where an acronym is used in the primary or secondary labelof an approximately determined landmark. Here the acronym would be included in capital letters, e.g.,Tower (USCG). The primary label would be shown in initial capitals only.


(STATE HOUSE) or BUILDING (RITZTOWER) or TOWER (CUSTOM HO) might beshown on secondary labels. Well-known andunusually prominent landmarks are, on occa-sion, depicted using the name of the landmarkas the primary label. For example, EMPIRESTATE BUILDING and WASHINGTONMONUMENT are shown on nautical charts.

Descriptive labels that identify the rela-tive size or location or other distinguishingcharacteristics of the landmark may also beshown in parentheses following or below theprimary name. When only one object of a groupof similar objects is charted, the descriptivelabel includes the number of objects in thegroup. Examples include STACK (TALLESTOF THREE), HOUSE (WEST GABLE), SIGN(L IGHTED) .

A descriptive label may also relate to theshape of the object. Examples include TANK(OBLONG), TANK (BALL), or TANK (BALLON TEE). Color is not normally noted5 in alabel because this may be only temporary.Painted names on objects are not normallyshown unless the name or abbreviation is dis-played in very large and conspicuous lettersthat are easily identified. The material of con-struction is not described in a secondary labelbecause the mariner usually cannot identifythe material from a distance.

In some cases both a secondary name anddescriptive label are included. For example:

STACK (FLARE)(TALLEST OF THREE)

might be found in a shore side petroleum re-finery.

The height of the object is also sometimesincluded. Heights can be used for determin-ing the vessel�s distance from the landmark(see Bowditch) and, with bearing data, to fixthe vessel�s position. In the case of landmarks,the height is given in feet (or meters for met-ric charts) measured from the top of the land-mark relative to mean high water except innontidal areas where these are measured rela-tive to the sounding datum. Height informa-tion is provided for only a minority of charted

landmarks, however.Aircraft obstruction lights are typically

regarded as secondary importance as an aidto navigation. Therefore, these are not nor-mally charted with a light dot and magentaflare unless listed in the Light List and givena Light List number. Obstruction lights onlandmark objects are not labeled unless spe-cifically requested by a reliable source. Inthis case, no differentiation is made betweenocculting and fixed lights. For example, astack (with accurate location) with a whitestrobe and red obstruction lights would belabeled:

STACK (STROBE, R LTS).An obstruction recommended for charting

as a landmark that is identified only as an air-craft obstruction light is charted with the ap-propriate landmark symbol and labeled:

OBSTN (R LT).Radio structures are labeled with the type

of function and height (when considered of sig-nificant importance for visual sighting). AMbroadcast stations will have the call letters andfrequency included in the label, as will otherstations known to be used for marine naviga-tion assistance. Here are a few examples:

RADIO MAST 862 FT(TV)(STROBE, R LTS)

RADIO MAST 483 FTW S S O1230 KHZ(R LTS)

RADIO TOWER 315 FT(FM, MICROWAVE)(R LTS)

In very congested areas, a list of stationsmay be provided elsewhere on the chart toavoid the elimination of important topographyand/or hydrography as a result of labeling.

The foregoing provides a useful summaryof key charting conventions for landmarks.

5Color may be included, however, in U.S. Coast Pilot or Light List descriptions.

Landmarks 6-11

�Other Sources of Landmark InformationIn most cases the position and the label(s)

shown on the chart will be sufficient for thenavigator to use the landmark for navigation.However, other sources may offer useful in-formation as well.

Pictures of selected landmarks are in-cluded on the back of certain conventional andsmall-craft nautical charts. These photographsare very useful in identifying landmarks. Forexample, the back of NOS Chart No. 13221(Narragansett Bay) contains several photo-graphs of landmarks and ATONs in the area.

Commercially produced cruising guides ofthe area sometimes provide descriptions and/or photographs of landmarks.

An important source of collateral informa-tion on landmarks is the U.S. Coast Pilot. Im-bedded in the general text and, in some areas,highlighted in a special section called �Promi-nent Features,� the U.S. Coast Pilot providesinformation on the location, appearance, andsuitability of landmarks for navigation. Guid-ance for the preparation and revision of theU.S. Coast Pilot is provided in the Coast PilotManual. Here is an excerpt from this docu-ment regarding how �Prominent Features�should be described:

�Prominent Features. Describe thebest charted landmarks for navigation,such as land formations, lights, tanks,stacks, towers, buildings, etc. Note thecolor, form, and height of headlandsand peaks. Streaks of color in bluffsmay be useful in identifying features.If objects such as mountains, hills, cliffs,islets, or rocks are recommended aslandmarks, give their measured or es-timated heights�.

� �In highly developed areas wherethere are numerous charted structures,the Coast Pilot supplements the chartsin two important ways: by identifyingthe best landmarks and by describingthe structures for positive identifica-tion. Give the height, color, and paint-ing pattern of prominent structures ifavailable. Describe the general shape

of unusual objects�.�

Here are a few passages from Volume 3, At-lantic Coast: Sandy Hook to Cape Henry (1993)that illustrate the type of information pre-sented:

� �When approaching Maurice River, mari-ners should use care and not confuse thestructure of East Point Light with a pri-vate house with a tower about 1.3 miles tothe east, both landmarks are similar inappearance.�

� �In 1967, the monument on Liston Pointwas reported destroyed; and in 1983, themonument on the south side of the entranceto Hope Creek was also reported de-stroyed. Remains of the structure fromListon Point may exist up to 100 feet off-shore and may be covered during hightide.�

� �A large, cylindrical water tank, about 1.5miles west of Ocean City Inlet, is promi-nent and is a good landmark while enter-ing the inlet.�

� �Assateague Light and the lookout toweron the southern tip of Assateague Islandare good marks for approachingChincoteague Inlet.�

� �Abandoned Navesink Lighthouse is in acleared space on the easternmost spur ata ground elevation of 180 feet; the two 73-foot brownstone towers, the north one oc-tagonal and the south square, are con-nected by a dwelling.�

As a final example, consider this descriptionof the entrance to Bridgeport, CT, harbor,taken from Volume 2, Atlantic Coast: Cape Codto Sandy Hook (1993):

�Prominent Features. The large redand white horizontally banded stack ofa power plant on Tongue Point is themost prominent landmark in this area.Other prominent landmarks include a


group of stacks on Steel Point: the tow-ers of a high-voltage line; several churchspires; a gas tank with a red-and-whitecheckered band at the top, on the westside of Pequonnock River; the radiotowers at Pleasure Beach; the Bridge-port Harbor Light 13A. The rays of anaerolight about 1.3 miles northwest-ward of Stratford Point can be seenfrom offshore.�

The U.S. Coast Pilot is invaluable as asupplement to nautical charts for many rea-sons. These few examples illustrate why thisis so for the identification of landmarks.

Practical Pointers and LimitationsRelevant to Landmarks

The balance of this chapter provides somepractical pointers relevant to the use ofcharted landmarks in navigation. The firstpart of this section presents practical ideason the selection of charts and landmarks fornavigation. The second part addresses theimportant topic of why some charted land-marks may not always be able to be seen (oridentified) from the vessel.

�PointersPerhaps the most important suggestion is

to select the largest scale chart of the area fornavigation. This point is made in severalplaces in this manual, but it is worth restat-ing here. Large-scale charts offer the great-est amount of detail for a small area, and offerthe greatest number of charted landmarks�hence the largest number of options for posi-tion fixing. Any landmark shown on asmall(er)-scale chart will also be shown on thelarge(er)-scale chart of the area, but many land-marks shown on large-scale charts are not de-picted on small-scale charts because it is nec-essary to generalize charted features fromlarge scale to small scale. As well, the latestedition of this chart�with corrections given inthe NM�should be used. Although landmarksare relatively permanent (recall that perma-nence is one of the criteria for charting a land-mark), they do change on occasion. Structuresare torn down, and new ones are periodically

constructed, so it makes sense to have the lat-est information at hand.

Another important point to reemphasizeis that all sources of information should beused to fix the vessel�s position�not just land-marks. Maintenance of a dead reckoning plot,use of depth information, ATONs, and othermeans should all be used. Knowledge of eventhe vessel�s approximate position can be help-ful in identifying landmarks that might be usedfor more exact fixes. Moreover, other informa-tion (e.g., the depth of water at the vessel�slocation) can be used to increase the confidencein�or rule out�the tentative identificationof a landmark.

�Selecting Landmarks For UseIn low-lying land areas of low population

density (e.g., portions of the Delaware and Vir-ginia coast) landmarks may be few and far be-tween, and the mariner may have little choiceas to which landmarks to use. Selection guide-lines for landmarks are not relevant in thiscase.

However, other coastal areas offer manymore charted landmarks, and the mariner of-ten has a choice of which to use for naviga-tional purposes. Here are four useful selec-tion criteria for suitable landmarks in caseswhere choices are available:

� Objects should be selected that are de-tectable and readily identifiable. Manyfeatures might be used for position fix-ing, but objects selected by cartogra-phers as landmarks are likely to be con-spicuous (see below). Landmarks de-picted with the accurate position sym-bols are to be preferred over those de-picted with the approximate locationsymbol. Refer also to the U.S. CoastPilot or commercially produced cruis-ing guides for information on the ap-pearance of conspicuous landmarks.

� Objects selected should be in a geo-metrical configuration suitable to theirintended navigational purpose. For ex-ample, if a landmark is to be used toestablish a danger bearing, it should be

Landmarks 6-13

Fig. 6-2. Excerpt from NOS Chart 13218 (Martha's Vineyard to Block Island). The TOWER(ABAND LT HO) off Sakonnet Point is ideally situated to define a danger bearing to avoid Schuyler

Ledge when approaching from the south. The accurately known landmark is likely to be conspicuous.Indeed, the lighthouse was probably there precisely for this purpose.

SUPPLEMENTAL INFORMATION Consult U. S. Coast Pilot 2 for important sup

plemental information.

83


Fig. 6-3. Excerpt from NOS Chart 13218 (Martha's Vineyard to Block Island). The DOME and S�PIPE nearWoods Hole would offer a poor crossing angle for a vessel attempting to fix its

position in the vicinity of the Middle Ground. Use of either landmarkand the CUPOLA at the east end of Naushon Island would be preferable.

/

72

\ ! /\

One-way traffic lanes overprinted on this chart are

~~t~~e~ ~~ ~~i~t~ i~~~I~~~. bfh~~1 ~:v~s~~~~r~~~~~~~ 0 to aid in the prevention of collisions at the approach to Narragansett Bay and Buzzards Bay but are not intended in any way to supersede or alter the applicable Rules of the Road. Separation zones are Intended to separate inbound and outbound traffic and to be free of ship traffic. S~paration zones should nqt be us~d except for crossing purpses. When crossing traffic lanes and separation zones use extreme caution

ANCHORAGE AREAS LOOKOUTTOWERO 110.140, 110.450 (see note A)

Limits and design of anchorage areas are shown i

Landmarks 6-15

appropriately positioned relative to thehazard to be avoided as illustrated infigure 6�2. If more than one landmarkis to be used�as, for example, to plot atwo or three bearing fix�the land-marks should be chosen so that the re-sulting crossing angles of the lines ofposition are best. For two objects, acrossing angle of 90° is optimal, andcrossing angles less than 20° or 30°should be avoided. (Refer to figure 6�3for an illustration.) For three objects,60° crossing angles are best. (Bowditch,Maxim.) Selection criteria for horizon-tal sextant angles are more complex,and the reader is directed to some ofthe references (Bowditch, AdmiraltyManual of Navigation) for details.

� Landmarks closer to the vessel are gen-erally preferable to those further away.This is because errors in bearing (takenwith a hand-bearing compass or radar)are nearly independent of the distance,and the position error associated witha given error in azimuth increases di-rectly with distance. If a compass bear-ing is inaccurate by 5° (a plausible fig-ure, see Dahl), for example, the linearerror is approximately 5,300 feet if thelandmark is 10 miles distant, but onlyabout 260 feet if the landmark is 1/2mile distant. (For more detail, seeDahl, Moody, or Brogden.)

� Taller landmarks should generally bechosen in preference to shorter objects.Other things being equal, taller objectscan be seen at a greater distance thanshorter objects due to the curvature ofthe earth. If He is the height of theobserver�s eye (in feet) and Ho is theheight of the object in the same units,then maximum distance, D (in nauti-cal miles), at which the object can beseen (as a result of the curvature of theearth (Bowditch)) is given by the equa-

tion, D = 1.17ÖHe + 1.17ÖHo.Assuming a height of eye of 10 feet, a20 foot object would be just visible overthe horizon at 8.9 nautical miles, a 100foot high object might be seen at 15.4nautical miles. (See table 3-1.) Ofcourse, use of this criterion dependsupon the height of the object beingknown and recorded on the chart.Height information is not provided forall landmarks and certain tall land-marks, such as radio towers, may bedifficult to see (Eyges) in hazy condi-tions because these are generally slen-der objects.

�LimitationsEven experienced mariners occasionally

have trouble detecting and identifying chartedlandmarks (Graves, Eyges). So it is worth-while to enumerate some of the reasons whylandmarks may not be seen. These include:

� The landmark may no longer be there.Although landmarks are selected so asto be relatively permanent, artificialstructures are occasionally destroyedby natural disasters or demolition ac-tivities. Ultimately, this fact is re-ported to NOAA and the chart is up-dated to delete the landmark, but thisprocess takes time, and even the latestcorrected chart of the area may show�phantom� landmarks.6 Along withdemolition, new construction may cre-ate problems regarding landmarks, be-cause new structures (see below) maybe confused with charted landmarks.

� The landmark may not be visible as aresult of horizon geometry (see above)or poor atmospheric visibility. Knowl-edge of the vessel�s approximate posi-tion and the prevailing visibility, as wellas the landmark�s height, can be help-ful in determining whether or not alandmark is likely to be visible. Statis-tical visibility data for various locations

6In cases where changes in landmarks are viewed as critical to navigation safety, landmark changes willbe reported in the NM. Such listing is relatively rare, however.


can be found in the U.S. Coast Pilot.These data can be useful for trip plan-ning purposes. Table 6-5, for example,shows the average annual number ofdays with visibility less than or equalto 1/4 mile for selected locations in theUnited States, ranked in descendingorder. In Nantucket, MA, for example,poor visibility occurs an average of 96days out of each year�approximatelyone day out of four. St. Croix, San Juan,Hilo, and Honolulu enjoy nearly totalfreedom from episodes of 1/4-mile vis-ibility. Data in the U.S. Coast Pilot alsoshow the distribution of reduced vis-ibility episodes by month. Figure 6-4shows this information plotted for Nan-tucket, MA. As can be seen, the worst

months at this location are June, July,and August.

• The landmark may be masked by otherstructures, terrain features, or vegeta-tion. At the time that an object is se-lected as a suitable object for chartingas a landmark, a determination is madethat it is �conspicuous.� However, inthe years since originally charted,events may have occurred which limitthe visibility of the object. For land-marks in built-up areas, such as cities,new construction may have taken placewhich masks the landmarks from someor all approach angles. In rural areas,trees or other vegetation may obscurethe structure�at least from some ap-

LOCATION

NANTUCKETBLOCK ISLANDSAN FRANCISCOTATOOSH ISQUILLAYUTEEUREKAATLANTIC CITYLOS ANGELESS E AT T L EASTORIAPORT ARTHURHOUSTONSAVANNAHWILMINGTONMOBILEPENSACOLASACREMENTOJACKSONVILLEPORTLANDNEW YORKDAYTONANEW ORLEANSHARTFORDBRIDGEPORTBALTIMORERICHMOND

STATE/TERRITORY

MARICAWAWACANJCAWAORT XT XGAD EALF LCAF LORNYF LLACTCTMDVA

ANNUAL DAYSWITH VSBY.

LESS THAN OREQUAL TO 1/4 M

9679645949494844434341414039393735353333323130303029

LOCATION

CORPUS CHRISTICHARLESTONSAN DIEGONEW HAVENAPALACHICOLABROWNSVILLEPROVIDENCEPHILADELPHIAWILMINGTONTAMPANORFOLKFT MEYERSBOSTONJUNEAUNEWARKCAPE HATTERASANNETTEWASHINGTONWEST PALM BEACHMIAMIKEY WESTST CROIXSAN JUANLIHUEHILOHONOLULU

STATE/TERRITORY

T XSCCACTF LT XR IPANCF LVAF LMAAKNJNCAKDCF LF LF LVIP RHIHIHI

ANNUAL DAYSWITH VSBY.

LESS THAN OREQUAL TO 1/4 M

29292828282725252424232323222019161387100000

SOURCE: U.S. COAST PILOT

Table 6-5.Annual Days With Visibility Less Than or Equal

to 1/4 Mile for Selected Locations Ranked in Descending Order

Landmarks 6-17

FIGURE 6-4. SEASONAL VARIATION IN THE NUMBER OF DAYS WITH REDUCED VISIBILITY AT NANTUCKET, MA:

SUMMER MONTHS ARE WORST AT THIS LOCATION

NUMBER OF DAYS WITH VISIBILITY < 1/4 MILE

20~------------------------------------~

~l~ :ilil

15 f-

10 f-1111

dEIT?i:i: ::. :.111.1 .. I .....,.,

~ --= Ill! :i: .. ::::.: .• ::'::. :':', ~ 5 - ~.i;.;.:'.i:.i ~:i: I11 ) i::: ~::ii

i~i~ r :r ... 1:! ... l.)~ t LE[ :~~ .:! .. ,l.,l .. ,l ::;: :::: { :~:~: ::::

I I .. ::.: .. : ... ,:,.I.: .. ::.i .. :,: .. i .... : I .: .. ,i: .. :::.::i: .. :· .:· .... :1.:·.1:,1.,·.: I ...... ,~~ ..... :,~~ .... :~~.:.,~~ .... :.~: ..... , I I , ..... :!::.::i ...... :!~.:.::~:: ~ .. ~:::.~:::.~:::,~:::.'

I ." .. ;.:.§ I :': ... ·.I.i I I -O~~I~~~~~,~}~,~~,~~,~::ii~~,i.~,~~,~~I~,~J~,~

JAN MAR MAY JUL SEPT NOV FEB APR JUN AUG OCT DEC

MONTH SOURCE: U.S. COAST PILOT


proach angles. (In this case, landmarksmay be visible in certain seasons�e.g.,winter�and not in others.) Rememberalso that landmarks are selected to bevisible from the sea, but not necessar-ily from all possible approach angles.(Inspection of terrain features and el-evations can sometimes help to iden-tify terrain masking.)

� The detectability of an object by visualmeans is a complex function of atmo-spheric visibility, background contrast,and lighting. Landmarks may be �cam-ouflaged� as a result of limited contrastwith background areas or because oflighting conditions at the time of obser-vation. (See Eyges for several illustra-tions.)

� The mariner may be disoriented andlooking in the wrong place on the chart.It is commonplace in navigation that itis much easier to determine your posi-tion if you already know where you are.On reflection this statement is not astrivial as it seems. A practical tip inidentifying landmarks is to plot thevessel�s dead reckoning position (orestimated position if one LOP is avail-able). Then, based on this position onthe chart, plot the bearings to each ofthe charted landmarks. Next (binocu-lars with a built-in compass are best)look along these plotted bearings forthe landmark. If the vessel�s assumedposition is nearly correct (and the vis-ibility is sufficiently great and the land-marks are above the horizon), the land-marks should be visible on bearingswithin a few degrees of those plotted.This technique will not work if thevessel�s position is grossly in error, butcan be very helpful otherwise. (Foradditional details, see Bright (1990).)

� The mariner may actually see the land-mark, but not be able to establish posi-tive identification. This may occur be-cause of confusion among several pos-sible objects (see below), but may alsooccur because of ambiguity over theidentity or appearance of the object.For example, the term �tower� may beused to describe many related but dif-ferent objects. Towers (not otherwisedistinguished) could include structuresas diverse as aircraft control towers,tall buildings (the John Hancock build-ing in Boston, MA), and abandonedlighthouses. (In some cases a second-ary label will be included to narrowdown the possibilities.) The marinershould study the definitions of each ofthe landmark terms to maximize thepossibility of correct identification.

� Finally, it sometimes occurs that sev-eral objects can be seen from the ves-sel, but it is not immediately apparentwhich is the charted landmark. Inother words, the landmark may be de-tectable but not identifiable. For ex-ample, only some of the many watertanks in the Philadelphia�Camdenarea are charted as landmarks. De-pending upon the vessel�s position, itis not always possible to identify whichare the charted landmarks. In suchcases the mariner is well advised tosearch for other identifiable landmarksthat could be used to fix the vessel�sposition. Even an approximate fix maybe sufficient to enable correct identifi-cation of the original landmark. Thistechnique is known as �shooting up��measuring the bearing of�each of sev-eral candidate landmarks and choosingthe one that provides a line of positionthat passes closest to the vessel�s posi-tion. (For additional details, see Mellor.)

Landmarks 6-19

The competent mariner regards each voy-age as a learning experience. In cases wherea landmark is missed, or misidentified, themariner should make every attempt to deter-mine the reason(s) why this occurred. If thereason is that the landmark was improperlycharted, the mariner should bring this matterto the attention of NOAA and USCG so thatappropriate corrections can be made. Everyerror offers the opportunity to learn a valu-able lesson.

Concluding CommentsLandmarks are very useful for coastal navi-

gation and serve to complement the system of

� � � � � � � � � � � � � � � � � � � � � � � � �

Exhortation to Apprentices of the Art of Navigation

�When so ever any Shipmaster or Mariner shallset forth from land out of any river or haven, dili-gently to mark what buildings, castles, towers,churches, hills, downes, windmills and other marksare standing upon the land�all of which, or manyof them, let him portray with his pen, how they bearand how far distant.�

A. Ashley, 1583, quoted in Naish

� � � � � � � � � � � � � � � � � � � � � � � � �

ATONs. Careful study of the chart conven-tions presented in this chapter and the defi-nitions presented here and in the Glossarywill pay dividends in improved navigationalskills. Student navigators�and that includesall of us�would do well to take the opportu-nity of comparing the chart presentation offamiliar areas with what is observable fromaboard the vessel. Finally, prudent marinersdo not rely on any one aid or technique fornavigation. The navigator should use all avail-able data (e.g., dead reckoning positions,AT0Ns, depth information, electronic positiondata, and visual or radar observation of land-marks) to navigate safely.


Bright, C., �Danger Bearings and TurningMarks,� Ocean Navigator, Issue No. 45,March/April 1992, pp. 69, et seq.

Bright, C., �Identifying Visual Targets,�Ocean Navigator, Issue No. 33, June 1990,pp. 63, et seq.

Brogden, B., �Accurate Bearings: How to GetBetter Visual Fixes for Coastal Naviga-tion,� Ocean Navigator, Issue No. 51, Janu-ary/February 1993, pp. 78, et seq.

Carr, M., �Update Charts For Coastal Pilot-ing,� Ocean Navigator, Issue No. 50, No-vember/December 1992, p. 33.

Dahl, N., The Yacht Navigator�s Handbook,Hearst Books, New York, NY, 1983.

Defense Mapping Agency Hydrographic/Topo-graphic Center. American Practical Navi-gator, An Epitome of Navigation(Bowditch), Publication No. 9, DMA StockNo. NV PUB 9 V1, Bethesda, MD, 1995.

Ellam, P., Yacht Cruising, W.W. Norton &Company, New York, NY, 1983.

Eyges, L., The Practical Pilot, Coastal Navi-gation by Eye, Intuition, and CommonSense, International Marine Publishing,Camden, ME, 1989.

Graves, F., Piloting, International MarineCompany, Camden, ME, 1981.

Human Technology, Inc. Desk ReferenceGuide: Specifications Unit, Chart and Map,Feature: Buildings. Report developed forNational Ocean Service, Charting and Geo-detic Services, Marine Chart Branch, Un-der Contract OPM-85-77, McLean, VA, Oc-tober 1985.

Human Technology, Inc. Desk ReferenceGuide: Specifications Unit, Chart and Map,Feature: Landmark. Report developed forNational Ocean Service, Charting and Geo-detic Services, Marine Chart Branch, Un-der Contract OPM-85-77, McLean, VA, Oc-tober 1985.

Kals, W. S., Practical Navigation, Doubleday& Company, Gordon City, NY, 1972.

Maloney, E. S., Chapman Piloting, 60th Edition,Hearst Marine Books, New York, NY, 1991.

Markell, J., Coastal Navigation for the SmallBoat Sailor, Tab Books, Blue Ridge Sum-mit, PA, 1984.

Maxim, L. D., Advanced Coastal Navigation,Second Edition, United States Coast GuardAuxiliary, Coast Guard Auxiliary NationalBoard, Inc., Washington, DC, 1990.

McClench, D. and D. B. Millar, Mixter�sPrimer of Navigation, Sixth Edition, VanNostrand Reinhold, New York, NY, 1979.

Mellor, J., The Art of Pilotage, SheridanHouse, Dobbs Ferry, NY, 1990.


Moody, A. B., Navigation Afloat, Van NostrandReinhold, New York, NY, 1980.

Naish, J., Seamarks, Their History and Devel-opment, Stanford Maritime, London, UK,1985.

Toghill, J., The Yachtsman�s NavigationManual, John DeGraff, Clinton Corners,NY, 1975.

U.S. Department of Commerce, Coast and Geo-detic Survey. Nautical Chart Manual, Vol-ume One: Policies and Procedures, SeventhEdition, Washington, DC, 1992.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration, Na-tional Ocean Service, and Department ofDefense, Defense Mapping Agency Hydro-graphic/Topographic Center. Chart No. 1United States of America Nautical ChartSymbols Abbreviations and Terms, NinthEdition, Washington, DC, January 1990.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration, Na-tional Ocean Service. Coast Pilot Manual,5th Edition, Rockville, MD, 1994.

References

Areas, Limits, Tracks, and Routes 7-1

CHAPTER 7

Areas, Limits, Tracks,and Routes

Introduction and OverviewThis chapter addresses areas, limits, tracks,

and route information provided on the nauti-cal chart. �Areas and limits� (referred to inSection N of Chart No. 1) refer to a collectionof charting practices (symbols, labels, andnotes) used to depict certain areas and lim-its of importance to the mariner. All these ar-eas have statutory or regulatory significance(e.g., the �three mile limit,� a COLREGS de-marcation line, or a designated anchorage),but most also pertain to navigation safety(e.g., a danger area or safety zone). �Track/route� information (referred to in Section Mof Chart No. 1) depicted on the nautical chartcontains guidance (or regulations) relevant tothe selection of routes and/or procedures tobe followed for safe navigation. This chapterprovides background, summarizes the utilityof area/limit/track/route features, describesthe charting conventions (e.g., symbols, labels,and notes), identifies other relevant sourcesof information (e.g., the U.S. Coast Pilot), andpresents practical pointers on how this infor-mation can be used by the prudent mariner.

No attempt has been made to enumerate allareas/limits/tracks/routes depicted on the nau-tical chart nor to provide an exhaustive discus-sion of the many legal and policy issues rel-evant to each. Instead, the chapter focusesupon those features likely to be of greatest po-tential relevance to the recreational and com-

mercial vessel operator. The omission of anycharted feature in this chapter does not relievethe mariner of the responsibility of complyingwith any applicable regulations.

As noted above, many of the charted fea-tures discussed in this chapter have statutoryor regulatory significance. This is a chart user�smanual, which provides general information onthe charting conventions and the types of regu-lations that may be applicable to designatedareas. It does not purport to give legal advicepertaining to any rules or regulations summa-rized herein. Mariners are advised to read care-fully the general and specific regulations appli-cable to these areas. If in doubt, the marinershould seek advice from competent authority orlegal counsel.

Many specialized terms used in this chap-ter are defined in the Glossary in appendixA. Names enclosed in parentheses (e.g.,Bowditch) denote references listed at the endof this chapter that contain additional rel-evant detail or useful general information.Letter and number designators in the subsec-tion titles and/or text (e.g., N 1.2) refer to sec-tions of Chart No. 1. It is recommended thatChart No. 1 be kept at hand when readingthis chapter.

Utility of This InformationIn most other chapters of this manual, a

separate section is included on the uses of the

� � � � � � � � � � � � � � � � � � � � � ��A collision at sea can ruin your entire day.�

Attributed to Thucydides,

Fifth century B.C. quoted in Heinl

� � � � � � � � � � � � � � � � � � � � � �


information presented. Because of the diver-sity of the features treated in this chapter,this utility is best discussed on an item-by-item basis. In broad terms, however, this in-formation is charted to alert the mariner tocertain dangers to navigation (e.g., danger ar-eas, safety zones) and/or to applicable legalrequirements when entering or using thesewaters.

Federally Regulated Areas(N 1.2, N 2.2, N 31)

Certain waters are subject to general andpermanent federal regulations, published in amulti-volume series termed the CFR. Themost pertinent portions of the CFR for chartusers are Title 33, Navigation and NavigableWaters, and Title 40, Protection of the Environ-ment. Federally regulated areas include dan-ger areas, seaplane operating areas, seaplanerestricted areas, restricted areas, safetyzones, defense areas, security zones, andregulated navigation areas (not otherwiseclassified). Although there are some differ-ences among these areas or zones, it is con-venient to discuss these as a group under thebroad rubric of federally regulated areas.

�Regulated Navigation AreasA regulated navigation area is a water area

within a defined boundary for which specificregulations (in addition to the NavigationRules) have been established. Regulated navi-gation areas (not otherwise classified) havebeen established in various areas of the watersof the United States. Regulated areas are es-tablished to prevent damage or marine casu-alties, to protect waterfront facilities, and tosafeguard ports, harbors, and the environment.The establishment of these areas is under thejurisdiction of the USCG or the USACE.

The phrase �regulated navigation area� issometimes used in a more general sense to in-clude all waters for which usage or entry re-strictions have been established. In this moregeneral sense, a regulated navigation area isan inclusive term encompassing many of theareas described below.

�Danger AreaAccording to official charting definitions

in the Desk Reference Guide, a danger area�

�...is a specified area above, below, orwithin which there may exist potentialdanger from military, civil, natural ormanmade sources. A danger area maybe categorized as a prohibited area, ex-ercise area, firing area, or missile testarea.�

An exercise area (also called a militarypractice area) is an area shown on chartswithin which troop, ship, or aircraft exercisesare carried out. A missile test area is an arearestricted so that missile range and reliabil-ity tests may be conducted by the military.When in use, missile debris may be depositedat frequent and irregular intervals. A firingarea is a military target area for bombing and/or gunnery practice. A prohibited area is adanger area shown on nautical charts withinwhich navigation and/or anchoring is prohib-ited except as authorized by appropriate au-thority. Danger areas are typically related topotentially hazardous military activity.

�Seaplane Restricted Areas/SeaplaneOperating Areas(N 13, N 14)

As the name implies, seaplane operatingareas and seaplane restricted areas refer todesignated areas containing seaplane bases.The Inland Navigation Rules normally appli-cable to seaplane operations are changed indesignated seaplane restricted areas. UnderRule 18 (Responsibilities Between Vessels),paragraph (d), of the Inland Navigation Rules,which applies to the conduct of vessels in sightof one another, �...a seaplane on the watershall, in general, keep well clear of all vesselsand avoid impeding their navigation. In cir-cumstances, however, where risk of collisionexists, she shall comply with the Rules of thisPart.�

Seaplanes are in �last place� in the normalright-of-way hierarchy. However, seaplane


restricted areas have been established wherethe conventional right-of-way hierarchyamong vessel types described in Rule 18 is al-tered and/or vessels are prohibited from en-tering. For example, in the seaplane re-stricted area described in 33 CFR § 162.15 inManhasset Bay, NY, the applicable rules(found in 33 CFR or in the U.S. Coast Pilot)read: �(1) vessels shall not anchor or moorwithin the restricted area� and �(2) all vesselstraversing the area shall pass directlythrough without unnecessary delay, and shallgive seaplanes the right-of-way at all times.�As a practical matter, seaplanes on the wa-ter are not highly maneuverable (they cannotoperate in reverse, for example, and �taxiing�or �sailing� a single-engine seaplane is not aneasy skill to acquire), a fact recognized in thenavigation regulations applicable to seaplanerestricted areas.

As the name implies, seaplane operatingareas are areas frequented by seaplanes. Theseaplane operating area designation is typicallyless restrictive than a seaplane restrictedarea�warning mariners of the anticipatedpresence of seaplanes in the area but not nec-essarily prohibiting entry or anchoring.

Although the number of seaplane operatingand restricted areas throughout the country isnot large, it is important for the mariner to beaware of the special rules which govern vesseloperations in these areas.

�Restricted Area (N 20)According to official charting definitions in

the Desk Reference Guide, a restricted area�

�...is a specified area designated by anappropriate authority and shown oncharts, above, below, or within whichnavigation is controlled in accordancewith certain specified conditions. Thesecontrol measures are employed to pre-vent or minimize danger or interferencebetween parties using the area.�

Restricted areas are typically associatedwith military or other federal (e.g., Federal

Correctional Institutions) installations. Fig-ure 7�1 provides an excerpt from NOS ChartNo. 12283 (Annapolis Harbor) which shows,inter alia, a restricted area in the vicinity ofthe U.S. Naval Academy (Anchorage areasshown in this illustration are discussed in alater section of this chapter.).

�Safety Zones/Defense Areas/SecurityZones

The Desk Reference Guide defines safetyzones, defense areas, and security zones as fol-lows:

�A safety zone is a water area and/orshore area to which, for safety or envi-ronmental purposes, access is limited toauthorized persons, vehicles, or vessels.It may be stationary and described byfixed limits, or it may be described as azone around a vessel in motion.

�A defense area is a sea area, usuallyincluding the approaches to and thewaters of important ports, harbors,bays, or sounds, for the control andprotection of shipping, for the safe-guarding of defense installations bor-dering on waters of the areas, and forprovision of other security measuresrequired within the specified areas. Itdoes not extend seaward beyond theUnited States territorial waters.

�A security zone is all areas of waterwhich are so designated by the Cap-tain of the Port for such time as hedeems necessary to prevent damage orinjury to any vessel or waterfront fa-cility, to safeguard ports, harbors, ter-ritories, or waters of the United Statesor to secure the observance of therights and obligations of the UnitedStates.�

Safety zones are defined to minimizesafety or environmental hazards associatedwith non-military activities. For example,


Fig. 7-1. Excerpt from NOS Chart No. 12283 (Annapolis Harbor) showing a restricted area,a prohibited anchorage, a naval anchorage, and two additional anchorages.


safety zones are typically established aroundfacilities (berths, moorings, gas or oil trans-fer areas) where hazardous materials, such asliquified natural gas (LNG) or liquified pe-troleum gas products, are handled orshipped. Safety zones are also establishedaround certain Outer Continental Shelf(OCS) oil and gas operations (see 33 CFRPart 147). Safety zones may be either perma-nent or temporary�but, for obvious reasons,only permanent safety zones are depicted onNOAA charts.

The purpose of a security zone is to safe-guard vessels, harbors, parks, and waterfrontfacilities from destruction, loss, or injury fromsabotage, or other subversive acts, accidents,or other causes of a similar nature. Securityzones are generally established around mili-tary facilities, such as ammunition depots(e.g., the Naval Ammunition Depot in the vi-cinity of Sandy Hook Bay, NJ), submarinebases, and submarine construction yards (e.g.,the waters of the Thames River near the Elec-tric Boat Division). As with safety zones, se-curity zones may be temporary or perma-nent�but only permanent security zones aredepicted on NOAA charts.

�Relevance to the MarinerKnowledge of the location, dimensions, and

rules and regulations applicable to these areasis important to the mariner for obvious reasonsof safety. Being hit by a stray round, torpe-doed, or involved in a collision with an LNGtanker is certainly no one�s idea of an interest-ing diversion during an otherwise routine voy-age. Moreover, the penalties for unauthorizedoperations in federally regulated areas can besubstantial, including seizure and forfeiture ofthe vessel, fines, and prison sentences.

�Charting PracticesThis section provides information on

charting practices and related information forfederally regulated areas. Charting conven-tions consist of a symbol and associated labelsand notes. With few exceptions, NOAA chartsshow only the type of regulated area, its lo-cation, and a CFR section number. Specificregulations applicable to the area are pro-vided elsewhere (e.g., 33 CFR or the U.S.Coast Pilot).

�Symbol (e.g., N 1.2, N 2.2, N 31)Danger area limits are charted with a

dashed magenta line. To emphasize the pos-sibility of danger in these areas, a magentascreened band may be added to highlight thedashed limit line.

Seaplane landing areas and seaplane re-stricted areas (N 13, N 14) are charted with asolid magenta line.

Restricted area limit lines are charted witha T-dashed magenta line.

Safety zone, defense area, and security zonelimit lines are charted with a dashed magentaline.1

A regulated area, not otherwise classified,is depicted by magenta dashed or T-dashedlimit lines. Figure 7�2 shows a regulated area(not otherwise classified) in the vicinity of theChesapeake Bridge Tunnel as shown on NOSChart No. 12221 (Chesapeake Bay Entrance).

These areas are charted with their exactgeographic limits as defined in 33 CFR.

�Labels and NotesLabels and notes are printed in magenta

italic type. Regulated areas are identified onthe chart only by the primary title of the area(e.g., labeled �DANGER AREA,� �PROHIB-

1Where a defense area, safety zone, or security zone line and the three-mile-limit line coincide, thethree-mile line takes precedence. The label is charted along the line.


Fig. 7-2. Excerpt from NOS Chart No. 12221 (Chesapeake Bay Entrance)showing a regulated area (not otherwise classified)

and other features of interest.


ITED AREA,� �SAFETY ZONE,� �DEFENSEAREA,� �SECURITY ZONE,� �REGULATEDAREA,� etc.), an alphanumeric designator forthe area (if one has been assigned), the CFRsection number, and a reference to standardnote A (shown below).

For example, referring to the excerpt fromNOS Chart No. 13218 (Martha�s Vineyard toBlock Island) presented in figure 5-3 (referto Chapter 5), the prohibited area in the vi-cinity of Nomans Land is labeled as follows:

PROHIBITED AREA334.70 (see note A)

The number 334.70 refers to the CFR sec-tion number which discusses this prohibitedarea. �Note A,� typically found in an unclut-tered land area on the chart, contains thestandard text,2

�NOTE A

Navigation regulations are publishedin Chapter 2, U.S. Coast Pilot ______.Additions or revisions to Chapter 2 arepublished in the Notice to Mariners. In-formation concerning the regulationsmay be obtained at the Office of theCommander, ____ Coast Guard Districtin ______, __, or at the Office of the Dis-trict Engineer, Corps of Engineers in_____, __.�

Blanks in the above note are filled in withthe appropriate information.

The regulations applicable to the specificregulated area are always found in Chapter2 of the indicated volume of the U. S. CoastPilot. (Except when specifically requestedby appropriate authority, these regulationsare not shown on the nautical chart, how-ever.)

�ExamplesHere is an excerpt from the text describ-

ing the prohibited area described in Section334.70 of 33 CFR as contained in U.S. CoastPilot Volume 2 (1993) Atlantic Coast: CapeCod to Sandy Hook:

� 334.70 Buzzards Bay, and ad-jacent waters, Mass.; danger zonesfor naval operations. (a) AtlanticOcean in vicinity of Nomans Land-(1)The area. The waters surroundingNomans Land within an area boundedas follows:

[geographic coordinates of area omittedin this citation]

�(2) The regulations. No vesselshall at any time enter or remainwithin a rectangular portion of thearea bounded on the north by a lati-tude 41° 16�00", on the west by longi-tude 70° 47' 30", or within the remain-der of the area between 1 Novemberand 30 April, inclusive, except by per-mission of the enforcing agency.

�(3) The regulations in this para-graph shall be enforced by the Com-mandant, First Naval District, andsuch agencies as he may designate.�

The textual description in the U.S. CoastPilot provides information on the geographiclimits of the area, applicable regulations, andthe enforcing agency. The text applicable tothis area in the U.S. Coast Pilot is relativelybrief. Entries for other areas are often moredetailed and may run to several pages. How-ever, the above excerpt illustrates the generalformat.

Many of the areas discussed in this sec-tion have general as well as specific regula-

2On NOAA charts, Note A is reserved for the note listing the publications that contain navigationregulations relevant to that chart; other charted notes begin with Note B or some other reference labeleven if there is no Note A on that chart.


tions that apply. For example, the generalregulations pertaining to a safety zone arefound in 33 CFR §165.23, shown below:

�Unless otherwise provided in thispart:

�a. No person may enter a safety zoneunless authorized by the COTP[Captain of the Port] or the DistrictCommander [USCG];

�b. No person may bring or cause to bebrought into a safety zone any ve-hicle, vessel, or object unless autho-rized by the COTP or the DistrictCommander;

�c. No person may remain in a safetyzone or allow any vehicle, vessel, orobject to remain in a safety zone un-less authorized by the COTP or theDistrict Commander; and

�d. Each person in a safety zone whohas notice of a lawful order or direc-tion shall obey the order or directionof the COTP or District Commanderissued to carry out the purposes ofthis subpart.�

Specific regulations may amend or extendthe above general regulations, and are foundin the CFR (or U.S. Coast Pilot) in a separatesection. Mariners need to consult both specificand general regulations.

As an example of specific rules pertainingto a safety zone, consider this entry from theU.S. Coast Pilot Volume 3 (1993) Atlanticcoast: Sandy Hook to Cape Henry describinga safety zone located in the Chesapeake Bay:

§165.506 Chesapeake Bay,Hampton Roads, Elizabeth RiverSouthern Branch Liquified Petro-leum Gas Carrier Safety Zone.

�(a) The waters within 250 feet fromthe port and starboard sides and 300yards from the bow and stern of a ves-

sel that is carrying liquified petroleumgas in bulk as cargo are a safety zonewhile the vessel transits the Chesa-peake Bay and Elizabeth River betweenThimble Shoal Lighted Buoy #3 andthe Atlantic Energy Terminal on theSouthern Branch of the ElizabethRiver.

�(b)Except as provided in paragraph (c)of this section, the general safety zoneregulations in §165.23 [also containedin this volume of the U.S. Coast Pilot]apply to the safety zone. Permission toenter the safety zone may be obtainedfrom the Captain of the Port or a des-ignated representative, including theduty officer at the Coast Guard Ma-rine Safety Office, Hampton Roads, orthe Coast Guard Patrol Commander.

�(c) A vessel that is moored at a ma-rine, wharf, or pier or is at anchor mayremain in the safety zone while a ves-sel carrying liquified petroleum gaspasses its location if the vessel re-mains at its moorage or anchorage dur-ing the period when its location iswithin the safety zone.

�(d) A vessel that has had liquified pe-troleum gas in a tank is carrying theliquified petroleum gas in bulk as cargofor the purposes of paragraph (a) of thissection, unless the tank has been gasfree since the liquified petroleum gaswas last carried as cargo.

�(e) The Captain of the Port, HamptonRoads will issue a Marine Safety Infor-mation Broadcast Notice to Marinersto notify the maritime community ofthe scheduled arrival and departure ofa liquified petroleum gas carrier.�

�Illustrative RegulationsTable 7-1 provides an illustrative list of

regulations which may be applicable to variousfederally regulated areas. In the example ofthe prohibited area near Nomans Land, entry


Table 7-1.

Illustrative Types of Regulations Applicable to Federally Regulated Areas.

Regulations are area-specific. Consult the current U.S. Coast Pilot forregulations pertaining to each individual area.

� Enforcement authority (agency, facility)

� Advance notification of restrictions (e.g., published in Notice to Mariners)

� Warning signals (e.g., patrol vessels, display of flags, low aircraft passes, etc.)

� Outright prohibitions to entry

� Requirements for expeditious passage

� Requirements to vacate area promptly upon warning

� Limits to entry (e.g., during exercise periods, during certain times of day, during certain seasons,etc.)

� Minimum separation distances from naval or other designated vessels

� Limits to activity (e.g., no loitering, no stopping, no anchoring, no trawling, no fishing, no towing, nodocking, no entry onto land, etc.)

� Maximum height (e.g., for vessels operating in restricted areas associated with certain coastalairports in circumstances of reduced visibility)

� Minimum equipment

� Requirements for a pilot on vessels larger than a specified displacement

is prohibited to all but authorized vessels onlyfor specific months of the year. Dependingupon the area, the duration of the prohibitionmay be only for certain times of day, certaindays of the year, only when actual exercises orvessel transits are taking place (when thearea is said to be �hot�), or at all times. Al-ternatively, entry may be permitted, but a re-quirement for expeditious passage, or a re-quirement to vacate the area promptly uponnotification may be imposed.

In the Nomans Land example, entry is for-bidden, in other areas entry may be permitted,but limits may be placed upon specific activi-ties of vessels while in the area (e.g., no loiter-ing, no stopping, no anchoring, no trawling, nofishing, no towing, no docking, no entry ontoland, etc.). Minimum separation distances (e.g.,from naval vessels or carriers of hazardouscargo) may also be mandated in these areas.

In some regulated areas (e.g., that shownin figure 7�1) yet other requirements may beimposed. These include requirements thatvessels drawing less than a specified draft

not enter certain channels (unless the vesselis crossing the channel), a prohibition on theentry of vessels above a designated size withimpaired maneuverability, technical require-ments on tows, requirements for operatingradar in vessels above a designated size dur-ing periods of reduced visibility, and require-ments for pilots with local knowledge aboardvessels greater than a certain size (e.g., 100gross tons).

Finally, the height of vessels permitted tooperate in the regulated area may be limited.The height constraint is applicable in certainrestricted areas associated with some coastalairports and is intended to lower the risk of col-lision with low-flying aircraft and reduce thepossibility of interference with navigationalequipment. For example, in the restricted area(33 CFR § 162.20) contiguous to La GuardiaAirport, Flushing, NY, no vessels with a heightgreater than 35 feet may enter whenever theprevailing visibility is less than 1 mile.

In cases where entry is prohibited only dur-ing times when the area is being used, the


U.S. Coast Pilot will indicate how notificationis given, either in advance (e.g., in the Noticeto Mariners), or shortly before the activitycommences (e.g., by display of warning flags,the presence of patrol vessels, low aircraftpasses, etc.).

�SummaryIt is a surprisingly common misconception

that federally regulated areas cannot be en-tered at any time. In fact, many of these areasare not denied (or at least not denied at alltimes) and these areas can be safely used if theprescribed regulations are followed. The mari-ner should consult 33 CFR or the U.S. CoastPilot to determine the restrictions to entry andother pertinent regulations. However, unlessthe specific regulations are consulted (e.g., asfound in 33 CFR or the U.S. Coast Pilot), theprudent mariner has no alternative but to re-main well clear of federally regulated areas. Donot radio the USCG with a request for real-time information on navigation regulations ap-plicable to, or the status of, these areas. Not allUSCG units have this information readilyavailable. The USCG will respond to written ortelephone inquiries, but does not necessarilyoffer �real time� response.

Civil ReservationsCivil reservations include a variety of non-

military areas such as state and nationalparks, reservations, wildlife preserves, wildliferefuges, marine sanctuaries, Indian reserva-tions, and similar specially designated areas.Generally, reservation areas are charted onlyif requested by the cognizant agency. Withcertain exceptions, these areas provide inter-esting background rather than informationrelevant to navigation. (These areas arecharted in blue, as noted below, so as to re-serve the use of magenta and black for chart-ing features that are of greater navigationalimportance to the mariner.) Mariners are ad-vised, however, to consult the CFR and othersources for any regulations applicable tothese areas.

As an illustration of one type of civil reser-vation, figure 7�3 provides an excerpt from

NOS Chart No. 12274 (Head of ChesapeakeBay) which shows, inter alia, a portion of theSusquehanna National Wildlife Refuge. Ap-plicable rules for operating in wildlife refugesand other regulations are given in 50 CFRParts 25, 27, and 32. These regulations in-clude the Navigation Rules, state regulations,and several additional regulations. The addi-tional regulations include a prohibition onleaving boats (outside of designated mooringor beaching areas) unattended for a periodgreater than 72 hours without the permissionof the refuge manager, a ban on use of gov-ernment-owned docks for loading and unload-ing of boats (except in emergency), specialrules for water skiing, regulations applicableto marine sanitation devices, and a variety ofspecial rules which limit or prohibit huntingand fishing activities. Some wildlife refugeregulations are site specific.


ing practices and related information for civilreservations. Charting conventions consist of asymbol and associated labels and notes.

�Symbol (N 22)Civil reservations are charted with a blue

long-short dashed line. A more prominent bluescreened band may be added to the inside edgeof the entire outline if needed to avoid confu-sion. For example, where different reservationsoverlap, the screened band may be used to de-note the reservation(s) of greater importance.

�Labels and NotesLabels and notes are printed in blue type.

If the boundary is chiefly in the water, italictype is used; if chiefly on land, conventionaltype is used. The label type should be consis-tent on overlapping charts. The label consistsof the name of the reservation (e.g.,�SUSQUEHANNA NATIONAL WILDLIFEREFUGE�) in italic capitals and a description(e.g., �protected area�) in lower case italic typeif appropriate. The label �see note A� is in-cluded only when the cited federal regulationsare given in the U.S. Coast Pilot. Where ref-


erence to note A is not appropriate, the labelmay refer to another note or the CFR.

�Relevance to the MarinerGenerally speaking, civil reservations are

of only limited interest to the mariner. Thisis reflected in the choice of color for their de-piction on the nautical chart. Nonetheless,these features are charted to alert the mari-ner to possible regulations which may affectentry and/or limit activities.

The U.S. Coast Pilot provides relevant in-

formation for some, but not all, of these ar-eas. Mariners interested in using these wa-ters should consult appreciable sections of theCFR. (Refer to the CFR Index to find the ap-propriate section(s).)

Federally Regulated Anchorage Areas/Grounds

Federally regulated anchorage areas andgrounds are important features depicted onNOAA charts. It is convenient to group fed-erally regulated anchorage areas into three

Fig. 7-3. Excerpt from NOS Chart No. 12274 (head of Chesapeake Bay) showinga restricted area and portion of Susquehanna National Wildlife Refuge.


broad classes: (i) anchorage grounds, (ii) spe-cial anchorage areas, and (iii) fairway anchor-ages. These are discussed below.

�Anchorage GroundsThe USCG is authorized (under Section 7

of the River and Harbor Act of March 4, 1915)to define and establish anchorage grounds forvessels �whenever it is apparent that these arerequired by the maritime or commercial in-terests of the United States for safe naviga-tion.� Further, the USCG is authorized to es-tablish rules and regulations applicable tothese designated anchorage grounds.

Several types of anchorage grounds havebeen established by the USCG, including (butnot limited to) general anchorages, commercialanchorages, deep-draft anchorages, small-craft anchorages, special anchorages, quaran-tine anchorages, temporary anchorages, dead-ship anchorages, explosive anchorages, forbid-den anchorages, nonanchorage grounds, andrestricted anchorages. For the most part,terms used to describe these anchoragegrounds (e.g., commercial anchorages) are notdefined explicitly in the CFR. Rather, the defi-nitions are implicit and made clear by thespecific rules and regulations pertaining toeach designated anchorage. For example, adead-ship anchorage is designed to lay upships for extended periods, a quarantine an-chorage is designed to accommodate ships re-questing quarantine inspection, a deep-draftanchorage is designed principally for deep-draft ships. Forbidden, prohibited,nonanchorages, and restricted anchorages allhave regulations which limit or prohibit an-choring by various types of vessels, or requirespecial authorization for anchoring. A de-scription of these designated anchoragegrounds and the regulations applicable toeach can be found in the CFR and the U.S.Coast Pilot.

Anchoring berths are usually circular ar-eas located within certain established anchor-age grounds as a convenience in assigning an-choring locations for both military and com-mercial vessels. Information concerning an-

choring berths may be published in the CFR(and U.S. Coast Pilot), but may also be devel-oped by local users and available from theoriginator.

�Special Anchorage AreasAn Act of Congress of April 22, 1940, pro-

vided for the designation of special anchorageareas wherein vessels not more than 65 feetin length, when at anchor, are not requiredto carry or exhibit anchor lights. These spe-cial anchorage areas (33 CFR § 109.10) are�well removed from fairways3 and locatedwhere general navigation will not endangeror be endangered by unlighted vessels.� Spe-cial anchorage areas are established for theconvenience of small (typically recreational)vessels.

�Fairway AnchoragesAccording to 33 CFR § 166.105, �shipping

safety fairway means a lane or corridor inwhich no artificial island or fixed structure,whether temporary or permanent, will be per-mitted.� These fairways are established to con-trol the erection or structures so as to providesafe approaches through: (i) oil fields in theGulf of Mexico to entrances to the major portsalong the gulf coast (33 CFR § 166.200), (ii) thecoast of California (33 CFR § 166.300), (iii) thecoast of Alaska (33 CFR § 166.400), and (iv)the Atlantic coast (33 CFR § 166.500). A fair-way anchorage �means an anchorage area con-tiguous to and associated with a fairway, inwhich fixed structures may be permitted withincertain spacing limitations.�

�Relevance to the MarinerKnowledge of the presence and location of

designated anchorage grounds/areas are rel-evant to the mariner for two principal reasons:

First, and perhaps most important,charting these areas serves to informthe mariner that various rules andregulations may apply to each desig-nated area. (Sources for these regula-tions are identified below.) Table 7�2

3Shipping safety fairways are also charted.


provides a sampling of some of thetypes of rules that may apply to any ofthese areas. In brief, there may be out-right prohibitions on anchoring, limitson the type, number, or duration ofstay of vessels in an anchorage, limitsor prohibitions on certain activitieswithin an anchorage (e.g., no lighteringor fishing), requirements to plot posi-tion and/or maintain a communicationsguard, notification requirements, andtechnological requirements (e.g., use ofmultiple anchors, requirements tohave tugs present, etc.). Not all of therestrictions identified in table 7�2 are

applicable to each anchorage, but eachof the rules are applicable to some ofthese areas. Failure to follow the rulescould entail significant operatingrisks, and may involve legal penaltiesas well.

Second, designated anchoragegrounds should alert the mariner toareas where anchored vessels may beencountered. Therefore, these areasare generally to be avoided, except byvessels intending to use the anchor-age. (By design, these designated an-chorage areas are not located in mainchannels, so avoidance is not particu-

Table 7-2Illustrative Regulations That May Pertain to Designated Anchorages

Regulations are anchorage-specific; not all anchorages will have each of the illustrativeregulations given. The current U.S. Coast Pilot should be consulted to find

the specific regulations applicable to each designated anchorage.

� Controlling authority and permit requirements

� Limits to type of vessel (e.g., recreational, commercial, naval, (submarines, aircraft carriers, de-stroyers, etc.) explosives, vessels under the custody of the United States, dead ships)

� Maximum or minimum length and/or draft of vessel

� Priority among vessels (e.g., priorities accorded naval vessels, commercial vessels, or vesselsawaiting quarantine inspection, etc.)

� Freedom from requirements to display anchor lights (for vessels less than 65 feet long in designatedspecial anchorages)

� Conditions of use (e.g., during emergencies only)

� Limits on navigation, transit speeds, or on certain activities (e.g., fishing, lightering, etc.)

� Cargo restrictions

� Limits on the number of vessels that can use an anchorage

� Prohibition of certain types of vessels (e.g., fishing vessels, vessels being dismantled)

� Minimum distances among anchored ships

� Limits on placement of anchors and requirements for multiple anchors

� Permission or limits on placement of moorings, floats, or buoys

� Notification Requirements (e.g., when anchoring, and prior to engaging in certain operations, orgetting underway)

� Maximum time to get underway (e.g., �warm start� capability, prohibition on �dead� ships, or require-ment that �dead� ships have tugs alongside)

� Requirements to maintain a communications guard and/or to plot position

� Requirements for wooden ships to have radar reflectors aboard

� Prohibitions on use by unseaworthy ships

� Time limits (e.g., 24-hours, 48-hours, 30-days)


larly burdensome.) In special anchor-age areas, vessels less than 65 feet inlength are not required to display an-chor lights, which means that vesselstransiting these areas at night are welladvised to exert special vigilance toavoid possible collisions with un-lighted vessels at anchor.


ing practices and related information for fed-erally regulated anchorages. Charting conven-tions consist of a symbol and associated labelsand notes. With few exceptions, NOAA chartsshow only the type of anchorage, its location,and a CFR section number. Specific regulationsapplicable to the area are provided elsewhere(e.g., 33 CFR or the U.S. Coast Pilot).

�Symbol (e.g., N 11.1 - N 20)Federally regulated anchorages are de-

picted by magenta limit lines which show theexact geographic boundaries of the anchorage.The line thickness and whether or not it is solidor dashed varies with the type of anchorage, asshown in table 7�3. A magenta screen may beadded for emphasis.

Anchoring berths (N 11.1, N 11.2) arecharted as solid or dashed circles of specifieddiameter with a small center-position circle(solid or dashed to correspond the berth limitsymbol) and a designator. Circles and designa-tors may be shown in magenta or a screenedgreen. (If another color is required for clarity,berths may be printed in black.)

Figure 7�4 provides an excerpt from NOSChart No. 12221 (Chesapeake Bay Entrance)showing two naval anchorages, a commercialexplosive anchorage, and an anchorage berth.

�LabelThe charted anchorage area is identified

with a magenta label in italic type that includesthe primary title of the area as given in theCFR, an alphanumeric designator (if as-signed), the CFR section number, and a ref-

erence to the standard note A discussed ear-lier in this chapter. Examples include:

SPECIAL ANCHORAGE110.1, 110.126a (see note A)

COMMERCIAL EXPLOSIVE ANCHORAGE110.168 (see note A)

FAIRWAY ANCHORAGE166.200 (see note A)

Bottom characteristics (see Chapter 4) are de-picted in designated anchorage areas and otherareas where vessels are expected to anchor.

�NotesAnchorage areas also refer to the standard

note A. This note directs the mariner to theappropriate section of the U.S. Coast Pilot.Applicable regulations can be found in eitherthe CFR or the U.S. Coast Pilot. Regulationsmay consist of both specific regulations appli-cable to the designated anchorage area andgeneral regulations (i.e., common regulationsapplicable to several anchorages in the samearea). For example, there are numerous gen-eral regulations applicable to Anchorage Eshown in figure 7�4. But there are additionalspecific regulations given in the CFR and theU.S. Coast Pilot. The specific regulations (33CFR § 110.168) include:

�(4) Anchorage E. (i) A vessel may not an-chor in Anchorage E without a permit issuedby the Captain of the Port.

�(ii) The Captain of the Port shall give com-mercial vessels priority over naval andpublic vessels.

�(iii) The Captain of the Port may at anytime revoke a permit to anchor in An-chorage E issued under the authorityof paragraph (f)(4)(i) of this section.

�(iv) A vessel may not anchor in AnchorageBerth E-1 unless it is carrying or handlingdangerous cargo or military explosives.


Table 7-3.Charting Symbols for Federally Regulated Anchorages

Type of Anchorage

Commercial anchorage

Dead-ship anchoragea

Deep-draft anchorage

General anchorage

Military anchorage

Small-craft anchorage

Special anchorage

Temporary anchorage

N/A

N/A

N/A

N/A

Navalb

Naval and General

N/A

N/A

N/A

Subtype (if defined) Charting Symbol

Explosive anchorage

Forbidden anchorage

Prohibited anchorage

Nonanchorage

Quarantine anchorage

Restricted anchorage

Commercial explosive

Emergency explosive

Naval explosive

Temporary explosive

N/A

N/A

N/A

N/A

N/A

0.2 mm dashed magenta line;anchoring berths may also beshown

Fairway anchorage N/A

0.2 mm solid magenta line;anchoring berths may also beshown

0.5 mm solid magenta line;anchoring berths may also beshown

�(v) A vessel may not anchor within 500yards of Anchorage Berth E-1 withoutthe permission of the Captain of thePort, if the berth is occupied by a ves-sel carrying or handling dangerouscargo or military explosives.�

Nonfederally Regulated Anchorages(N 12.1)

State and local governments may estab-lish anchorages in waters under their juris-diction. These areas may also be charted atthe discretion of NOAA. Chart conventions

SOURCE: Adapted from information given in the Nautical Chart Manual

NOTES:a See: e.g., 33 CFR § 110.158.b Some naval anchorages are further subdivided into submarine anchorages (33 CFR § 110.150), aircraft

carriers, destroyers (33 CFR § 110.182), small craft (33 CFR § 110.159), or emergency naval anchorages(33 CFR § 110.155).


parallel those for federally regulated anchor-ages, except that a black dashed line is usedrather than a magenta line. Applicable rulesand regulations for these areas are not pub-lished in the U.S. Coast Pilot, but must be ob-tained by the agency having jurisdiction overthe anchorage area.

Harbors of Refuge (N 10)Harbors of Refuge are recognized anchor-

age areas without defined limits. These har-bors provide passing vessels with good hold-ing ground and temporary refuge fromstorms. For this reason, vessel operations(particularly operators of small vessels)should be familiar with the location of the

various Harbors of Refuge along a proposedroute. A harbor of refuge may or may not beconsidered a part of a shipping port. A har-bor of refuge is identified with a black anchorsymbol (N 10) and a label �HARBOR OF REF-UGE� in black italic capital letters.

Dumping/Disposal AreasDumping/disposal areas have been estab-

lished for various purposes, such as for oceandumping of toxic wastes (now prohibited) ordepositing dredged materials. These areasmay constitute hazards to navigation and arecharted for this reason. Three general classes(determined by the federal regulatory author-ity that has jurisdiction over their establish-

Fig. 7-4. Excerpt from NOS Chart No. 12221 (Chesapeake Bay Entrance) showinga variety of anchorages and berths along with other features of interest.


ment) of dumping areas are shown on NOAAcharts. These are briefly described below.

�EPA�Established Dumping Areas(N 24, N c, N d, N g)

The U.S. Environmental Protection Agency(EPA) established ocean dumping sites (40 CFRPart 227) for the purpose of disposing of toxicand nontoxic materials including dredged ma-terial, industrial waste, acid waste, municipalwaste, sludge, etc. These areas are charted inall cases where hydrography and other naviga-tional detail are shown in the area.4

Dumping areas designated in 40 CFR §228.12 are shown by a black dashed limitline. A label is added in black to identify thearea in italic type, capital and lowercase let-ters, in a size appropriate to the charted fea-ture. A label refers to note S. A descriptiveterm such as �dredged material� may beadded to the label to reflect the primary useof the area as identified in the regulations.Examples include:

Dump Site(see note S)Dump Site

(dredged material)(see note S)

Note S is charted in the vicinity of note Aand states;

�NOTE SRegulations for Ocean Dumping Sitesare contained in 40 CFR, Parts 220-229.Additional information concerning theregulations and requirements for useof the sites may be obtained from En-vironmental Protection Agency��

Hydrography and tints (see Chapter 4)

are retained in the dumping areas becausethese areas are not intended to interfere withnavigation. The date of the hydrography isstated as follows:

�Depths from survey of _____�

On small-scale charts, the dimensions of thedump site may preclude its being charted toscale. In this event, a minimum-size symbol (a2.0 mm dashed square) is used in lieu of at-tempting to depict the actual size. If this sym-bol is used for all dump sites shown on a par-ticular chart, these are identified by label, with-out reference to note S, e.g.:

Dump Site(dredged material).

�Navy�Established Dumping AreasThe Navy designated certain areas, gen-

erally in deep water at a considerable dis-tance offshore, for disposal of ammunition,chemicals, and explosives. These areas areshown on NOAA charts to inform chart us-ers, notably trawlers, who might tangle withdangerous materials. The same chart con-ventions are used as for Environmental Pro-tection Agency (EPA)�established dumpingareas.

�U.S. Army Corps of Engineers AreasThe USACE has authority to establish

dumping areas with the approval of EPA.These dumping areas are classified variouslyas spoil areas, disposal areas, or dumpinggrounds. The following note is added in blackto all charts containing spoil areas, disposalareas, and dumping grounds where dumpingis regulated by this agency:

4Refer to Chapter 4 for information on areas where hydrography is omitted.


�DUMPING CAUTION

Dumping dredged or fill materials inspoil areas, disposal areas, and dump-ing grounds is illegal without authoriza-tion from the U.S. Army Corps of Engi-neers. Regulations and permission fordumping in area (or areas) charted, maybe obtained at the office of the DistrictEngineer, Corps of Engineers, New Or-leans, Louisiana.�

Spoil areas (N 62.1) are established for thedisposal of dredged material removed from thebottom of channels and harbors during dredg-ing operations. If inactive, the area is stillcharted, but labeled in black italic capital andlower-case letters, �Discontinued Spoil Area.�These areas are generally located near and par-allel to the dredged channel and are potentiallydangerous to navigation. Active spoil arealimits are shown by a black dashed line de-lineating the extent of the area, a label (initalic, capital and lowercase letters) �SpoilArea,� with blue tint No. 1 added to accentu-ate their potentially dangerous nature. Spoilareas that uncover are tinted green. Sound-ings and depth curves (see Chapter 4) areomitted within spoil areas, although isletsand areas bare at MLLW are charted.

Disposal areas (N d) are established or ap-proved (see 33 CFR Parts 323-324) for depos-iting dredged material in waters where exist-ing depths and currents indicate that thedumping will not cause sufficient shoaling tocreate a danger to surface navigation. Disposalarea limits are shown by a black dashed line,except that soundings, tints, and depth curvesare retained inside the limits of these areas.The following note is shown in italic type:

�Disposal AreaDepths from survey of ______�

�Dumping Grounds (N c)Dumping grounds are areas formerly des-

ignated by the USACE (under 33 CFR Part

205, now revoked) for dumping (by permit)various types of materials. These dumpinggrounds are typically located well offshore indeep water.

Dumping ground area limits are shown bya black dashed line. Soundings and depthcurves may be charted within the limits. Ablue tint is added when justified by the chartedhydrography (see Chapter 4). Finally, the la-bel �Dumping Ground� in black italic type(capital and lower-case letters) is added in-side the limits of the area.

�Relevance to the MarinerGenerally speaking, these areas are de-

picted on nautical charts to alert the marinerto the possibility of danger when transiting thearea (e.g., spoil areas) or when engaging in cer-tain activities (e.g., trawling in the vicinity ofNavy-established dumping areas). Depiction ofthese areas on the nautical chart also serves toalert the mariner to the types of vessels thatmay frequent these areas. A spoil area, for ex-ample, might be frequented by dredges, tugs,and barges.

Spoil areas are of particular concern, be-cause of their generally shallow depths andproximity to dredged channels. There are nu-merous instances of vessels running aground inthese spoil areas. Avoidance is the safest courseof action lest they spoil your voyage in moreways than one.

�IllustrationFigure 7�5 shows an excerpt from NOS

Chart No. 11361 (Mississippi River Delta)showing the Southwest Pass at the mouth ofthe Mississippi River. Several features of thischart excerpt are of interest. Note the oil plat-forms, oil pipelines, and the safety fairway forvessels entering and existing the SouthwestPass. Note also the blue tinted spoil area on ei-ther side of the channel. The blue tint alertsmariners to the danger posed by these areas.See also the dump site to the west of the chan-nel. The northern portion of the dump site over-lays the spoil area. The cartographer electedto tint the entire dump site area blue, to em-phasize the possible dangers in this area.


Fig. 7-5. Excerpt from NOS Chart No. 11361 (Mississippi River Delta)


However, soundings south of the southernboundary of the original spoil area were re-tained, as these were judged unlikely tochange materially as a result of the dumpingactivities. This area was the site of a collisionbetween a northbound Dutch cruise shipNoordham and a southbound freighter Mt.Ymitos in November of 1993 (see ProfessionalMariner, Issue No. 5). The accident investiga-tion is still pending as of this writing, so itwould be premature to speculate on the causeof the accident. However, one aspect of thiscollision is of interest here. The Captain ofthe southbound Mt. Ymitos reportedly claimedthat he could not alter course to the right (i.e.,westward) because of the proximity of thedump site. Moving westward of the buoyedchannel when north of the fairway buoy �SW�would entail some risk of grounding. For po-sitions south of this buoy, the soundings andthe included 120-foot depth curve shown onthe chart offer more comfort. Presumably, anyvessel of sufficient draft to be accommodatedin the channel (40 feet) could transit this areawithout appreciable risk of grounding.

COLREGS Demarcation Line (N a)A COLREGS demarcation line (see 33

CFR Part 80) divides U.S. waters into two ar-eas. Landward of this line the Inland Naviga-tion Rules apply, seaward of this line the In-ternational Navigation Rules apply. (TheUSCG publishes both sets of rules inCOMDTINST M16672.2B, see references.) Al-though many of the navigation rules are com-mon to both sets, some differ. For example, re-quired lights and whistle signals under the in-land rules differ from those under the inter-national rules. For this reason it is importantthat the mariner be aware of the water areaswhere each set of navigation rules apply. TheCOLREGS demarcation lines are published inCFR and in COMDTINST M16672.2B in termsof the latitude and longitude of linear seg-

ments, but these coordinates are not conve-nient for use. For this reason, the COLREGSdemarcation lines are printed on NOAAcharts.

�Charting PracticesCharting conventions for COLREGS de-

marcation lines consist of a symbol, label, andnote, as discussed below.

�Symbol (N a)COLREGS demarcation lines are shown

on all coastal series charts (scale 1:150,000 andlarger) and on other charts as needed using amagenta dashed line (N a).

�LabelThe label �COLREGS DEMARCATION

LINE� in magenta italic capital letters (see fig-ure 7�2 or figure 7�5) is placed along the line,either inside or outside as space permits. If la-bels cannot be placed along the COLREGS line,these may be placed on land and parallel to thechart base. Labels in other locations (wherespace is limited) where labeling may be criticalare abbreviated �COLREGS.� This abbreviatedlabel may be omitted in cases where the labelswould be extremely close together or where sev-eral chart lines are in close proximity.

Some charts depict only areas where theinternational rules apply. This includes certainareas of New England, Florida, Puerto Rico,the Aleutians, and other areas. The followingnote is added to these charts in lieu of the ad-dition to the Symbols and Abbreviations note:

�COLREGS, 80.____ (see note A)International Regulations for Preventing

Collisions at Sea, 1972"

In areas where COLREGS lines are shownand space permits, the second line of the labelshows the CFR section number and the refer-ence to note A, e.g., �80.325a (see note A).�


Degaussing Range (N 25)5

A degaussing (demagnetizing) range is anarea within which a vessel�s magnetic field maybe measured. These measurements are used todetermine the required degaussing coil currentsettings and other corrective action(s). Sensinginstruments and cables are installed on the seabed in the range, with the cables leading fromthe range to a control position ashore. Thisrange is usually marked by distinctive buoysidentifying the purpose of the range. Althoughthere are relatively few degaussing ranges,their presence and location are relevant to themariner because of the specific rules and regu-lations that may apply therein. These include(but are not limited to) a prohibition on the in-troduction of external magnetic field sources,anchoring, trawling, and a requirement toavoid the range when it is in use. For an in-teresting article on the use of the degaussingrange, see Ryan.

The limits of the degaussing range areshown by a dashed line (N 25). Submarinecables extending from the shore are charted intheir exact position and shown in magenta. Thelabel �DEGAUSSING RANGE� is shown inblack capital italic letters in a type size appro-priate to the feature.

Maritime BoundariesThere are numerous maritime boundaries

(e.g., the Three Mile Line) referred to in stateor federal laws. (A description of the provisionsof the various laws having maritime bound-aries is beyond the scope of this manual. Thereader is referred to other sources for this in-formation.) The shoreline and the low-waterline are used as �baselines� for determining thevarious maritime boundaries described bygeographic coordinates in legal references.The nautical chart is the legal graphic author-ity for most of these boundaries.

Maritime boundaries reference to the low-water line that are found on NOAA charts in-clude the following:

Exclusive Economic Zone (200 nauticalmiles)

Magnuson Fishery Conservation andManagement Act Amendments(Alaska fishing limits)

Marine SanctuariesNational ParksNational SeashoresNatural Resources Boundary (3 leagues

or 9 nautical miles; Texas, Florida-Gulf of Mexico coast, Puerto Rico)

Political BoundariesTerritorial Sea and Contiguous Zone (12

miles)Three Nautical Mile LineState Parks.

Some of the more important of theseboundaries are explained below.

�International Boundaries (N 40, N 41)International boundaries are charted with

a solid black crossed dashed line (N 40, N 41).

�Exclusive Economic Zone (N 47)In 1983, a 200-mile Exclusive Economic

Zone (EEZ) was established. This zone is de-scribed in the Coast Pilot Manual as follows:

� �the EEZ of the United States is azone contiguous to the Territorial Seaand Contiguous Zone (12 nauticalmiles) of the United States, the Com-monwealth of Puerto Rico, the Com-monwealth of the Northern MarianaIslands (to the extent consistent withthe Covenant the United NationsTrusteeship Agreement), and theUnited States overseas territories andpossessions. The EEZ extends to adistance 200 nautical miles from thebaseline from which the breadth of theterritorial sea is measured��

5Some degaussing ranges (e.g., 33 CFR § 334.870) are also restricted areas.


The significance of this zone is describedin the Coast Pilot Manual as follows:

�Within the EEZ, the United States hasasserted, to the extent permitted by in-ternational law, (a) sovereign rights forthe purpose of exploring, exploiting, con-serving and managing natural re-sources, both living and nonliving, of theseabed and subsoil and thesuperadjacent waters and with regardto other activities for the economic ex-ploitation and exploration of the zone,such as the production of energy fromthe water, currents and winds; and (b)jurisdiction with regard to the establish-ment and use of artificial islands, andinstallations and structures having eco-nomic purposes, and the protection andpreservation of the marine environ-ment.

�Without prejudice to the sovereignrights and jurisdiction of the UnitedStates, the EEZ remains an area beyondthe territory and territorial sea of theUnited States in which all states enjoythe high seas freedoms of navigation,overflight, the laying of submarinecables and pipelines, and other interna-tionally lawful uses of the sea.�

The seaward boundary of the EEZ is coin-cidental with that of the Fishery ConservationZone (FCZ) over which the United States ex-ercises exclusive fishery management author-ity over all species of fish, except tuna.

The EEZ limit is shown by a black screenedline interspersed at regular limits by a �fish�symbol (N 47). This line is labeled �EXCLU-SIVE ECONOMIC ZONE� in black italic capi-tal letters.

�Closing Line/Three Nautical Mile Line/Territorial Sea and Contiguous Zone(N 42, N 43, N 44)

The closing line (baseline) is the dividingline between inland waters and marginal seasacross the entrance of a bay. The Three Nauti-cal Mile Line marks the boundary of the wa-ters within a three-mile zone adjacent to thecoast and seaward of the closing line. The Ter-ritorial Sea and Contiguous Zone marks theboundary of the waters within a 12-nauticalmile zone adjacent to the coast and seaward ofthe closing line.

Each of these lines are black screened un-broken lines of 0.5 mm lineweight. These linesare labeled in black italic type as follows:�THREE NAUTICAL MILE (see note X),��TERRITORIAL SEA (see note X),� and �TER-RITORIAL SEA AND CONTIGUOUS ZONE(see note X).�

The text of note X differs slightly accordingto whether or not the natural resources bound-aries of Puerto Rico or the gulf coast areshown. One version of this note is as follows:

�NOTE XThe 12-nautical mile territorial sea

was established by Presidential Procla-mation 5928, December 27, 1988, and isalso the outer limit of the U.S. contigu-ous zone for the application of domesticlaw. The 3-nautical mile line, previ-ously identified as the outer limit ofthe territorial sea, is retained becausethe proclamation states that it does notalter existing State or Federal law.The 9 nautical mile natural resourcesboundary off Texas, the Gulf coast ofFlorida, and Puerto Rico, and the 3nautical mile line elsewhere remainthe inner boundary of the Federal fish-eries jurisdiction and the limit ofstates� jurisdiction under the Sub-merged Lands Act (P.L. 83-31; 67 Stat.


Fig. 7-6. Excerpt from NOS Chart No. 12221 (Chesapeake Bay Entrance) showinga variety of features of interest, including a traffic separation scheme

and a Three-Mile Limit Line.

29, March 22, 1953). These maritimelimits are subject to modification, asrepresented on future charts. The linesshown on the most recent chart edi-tion take precedence.�

Figure 7�6 provides another excerpt fromNOS Chart No. 12221 (Chesapeake Bay En-trance) showing a Three-Mile Limit Lineamong other features of interest.


Traffic Separation Schemes and RelatedMatters

TSS and Vessel Traf f ic Services (VTS)are related systems used to aid in the pre-vention of collisions in the approaches tomany major harbors.6 Briefly, a TSS con-sists of a series of �highways in the water�that segregate traf f ic , whi le a VTS is aland-based system which provides adviceand control of part ic ipat ing vessels in amanner s imi lar to�but less e laboratethan�the system employed for air traff iccontrol. Centers for VTS have communica-tions equipment and radar and optical sys-tems for observation. TSS and VTS are dis-cussed in 33 CFR Part 161 (Vessel TrafficManagement) and 33 CFR Part 167 (Off-shore Traf f ic Management Schemes) . Al lvessels are obliged to follow Rule 10 (In-ternat ional Navigat ion Rules) regardingTSS, and there are specific rules and regu-lations (including whether participation inan associated VTS is voluntary or manda-tory) applicable to each area. (Refer to theU.S. Coast Pilot or 33 CFR for details.)

A TSS is a routing measure designed toseparate opposing streams of traffic by the es-tablishment of traffic lanes. Vessels need notuse a TSS (i.e., participation is voluntary).However, under Rule 10, paragraph (h), �...avessel not using a traffic separation schemeshall avoid it by as wide a margin as is prac-

ticable.� A TSS may include traffic lanes,separation zones, roundabouts, precaution-ary areas, inshore traffic zones, deep-waterroutes, areas to be avoided, and (in the caseof a corresponding VTS) calling-in points. Itis convenient to include pilot boarding areasin this section. Definitions and chartingpractices are described below. Figures 7�7and 7�8 provide excerpts from Chart No. 1which illustrate many of the chart symbolsused to depict TSS/VTS features. Figure 7�6 depicts a TSS in the vicinity of ChesapeakeBay, which includes traffic lanes, separationzones, and a precautionary area. This ex-cerpt also shows a pilot boarding area.

A traffic lane means an area within de-fined limits in which one-way traffic isestablished. When joining or leaving atraffic lane (Rule 10 paragraph (b) (iii))vessels are required to do so at as smallan angle as possible. As far as practi-cable, vessels should avoid crossingtraffic lanes (Rule 10 paragraph (c)).However, vessels crossing a trafficlane should do so on a heading asnearly as practicable at right angles tothe lane. Vessels are encouraged tonavigate at or near the center of thetraffic lane. Otherwise (see Cockcroftand Lameijer),

6Although it is convenient to discuss TSS and VTS in the same section, as both relate to routing andemploy similar charting conventions, it is important to distinguish between these two systems. A TSS is aset of �paper� conventions (routes) established by the host country in consultation with the InternationalMaritime Organization (IMO). (The IMO (formerly IMCO) is an organ of the United Nations, based in Lon-don, England, established to deal with recommendations relative to maritime safety and pollution.) A TSSis the subject of Rule 10 of the International Navigation Rules. A VTS, however, is a physical entity, con-sisting of a control facility termed a Vessel Traffic Center (VTC), manned by personnel from the host coun-try (principally the USCG in the United States, although a new private VTS has been commissioned in LosAngeles/Long Beach, CA, and others are planned for Tampa, FL, and Philadelphia, PA), communicationsfacilities, and systems of observation (television cameras and radar) and operates in accord with publishedrules and regulations (CFR) under Rule 10 of the Inland Navigation Rules. Some major harbors and harborapproaches (e.g., New York) have a TSS and a VTS. Others (e.g., the approaches to the Chesapeake orDelaware Bays) have only a TSS. Yet others (typically those entirely within inland waters, e.g., the St MarysRiver) have a VTS, but no TSS (although routing regulations are published for this area). Finally, mostharbors and harbor approaches have neither a TSS nor a VTS.


�...there is danger that a vesselwhich sets a course near the edgeof a lane will stray into the sepa-ration zone or the traffic lane des-ignated for traffic proceeding inthe opposite direction.�

Vessels should also keep clear of theouter limit of the traffic lane lying onthe vessel�s starboard side,

�...particularly if this line sepa-rates the lane from an inshorezone which is likely to contain traf-fic moving in the opposite direc-tion. On the edge of the lane twopower-driven vessels meeting onreciprocal courses would each berequired to alter course to star-board by Rule 14. Such action maycause both vessels to be involvedin further meeting situations mak-ing it difficult for them to returnto their correct lane or zone.�

Natural obstacles, including those form-ing separation zones may constitute aboundary. Traffic lanes are depicted innautical charts by a distinctive symbol(M 13). Arrows are drawn to indicatethe general direction of flow. If the traf-fic lane is wider than 5.0 mm at chartscale, the arrows are staggered withinthe lane. If not, arrows are placed inthe center of the lane. A label �IN-BOUND,� or �OUTBOUND,� may beadded in magenta capital italic type asshown in figure 7�6.

A separation zone or line means a zoneor line which separates the ships pro-ceeding in opposite or nearly oppositedirections; or separating a traffic lanefrom the adjacent sea area; or separat-ing traffic lanes designated for particu-lar classes of ships proceeding in thesame direction. Separation lines arerepresented by a magenta-screened

line at least 3 mm wide. Figure 7�6shows a separation zone in the easterninbound-outbound approach to Chesa-peake Bay.

A roundabout is a routing measure com-prising a separation point or circularseparation zone and a circular trafficlane within defined limits. Traffic withinthe roundabout is separated by movingin a counterclockwise direction aroundthe separation point or zone. A round-about is depicted by a unique symbol (M21, M d). As of this writing, there are noroundabouts in U.S. waters

A precautionary area means a routingmeasure comprising an area within de-fined limits where ships must navigatewith particular caution and withinwhich the direction of traffic flow maybe recommended. A precautionary areais depicted by a unique symbol (M 16,M 24), and may include a label, �PRE-CAUTIONARY AREA,� in magentaitalic capital letters. Figure 7�6 showsa precautionary area near the entranceto the Chesapeake Bay. Note that ves-sels not using the TSS may enter theprecautionary area. In the TSS shownin figure 7�6, many vessels (e.g., recre-ational, tugs with barges, etc.) enteringthe Bay from the north or south alongthe coast�and not using the TSS�rou-tinely enter this precautionary area.

A deep-water route is a route in a des-ignated area within definite limitswhich has been accurately surveyedfor clearance of sea bottom and sub-merged obstacles as indicated on thechart. A deep-water route may be ei-ther one-way or two-way. It is labeled,�DEEP WATER ROUTE,� or �TWO-WAY DEEP WATER ROUTE,� in ma-genta italic capital letters. Note thetwo-way deep-water route in thesouthern approach to Chesapeake Bayshown in figure 7�6.


Fig. 7-7. Excerpt from Chart No. 1 Showing Charting Conventions for Routing Measures.

Examples of Routing Measures \

\\ \

~=== - \ Q ---------_/ .~ -----~----7 [:> @ <:::>°OOD- 1

- __ \:) '-J <::> I

-~------ ~ « ----------_ ... , "

)

Q <J::::==::::::, ~

=====e>

Inshore traffic zone

11 1 1

Inshore

1 ~ lPRW 1

~ ~\ IJ ~RW ' -----1 a

1 ! ~~~~~ 1 __ --------

<F=== <:; 6 <:=== <:==== <:====

===V> <8 __ ~:::;~=~::-: ----!1 ~r :----------__ - / <:;::::;:::; __ - ..... v 1

__ - / ,, __ - -"" ..... 1

===t> ====t> ====t>

.. - c? / ".~ ,"'" 0 --- -------~ / , ~ s-,,) --.;_------ <= '= Pr~autjonary Or "T""T""T""T""T" "T"

;;/", _;;==-~- <)==== I ~ A,.. <l='9-== , ____ h ~ - - .,.... _ - - (see note) 1 t< L'). ~

,,,,'" ty?' ",," ______ - - ___ .:::::::: 18+ .. z:():).j t;:;\ ~ • _~ ;;' __ ""~ I ,~ \J f

<?,,_---" --__ =_=AF=t> ~ ,," ,...s.z... - - - - - - .., ~

<F=== @ <,,--------------

..... '- __ ~o.way deep water route 1 ------____ .J

====t>

------->~-------DW----

DW--

===--t> "( "(

"( "(

I

---> "( ------ DW-> --- "( ---- < > "( - -- ----- DW-<--> - "("(


Fig. 7-8. Legend for Figure 7-7

8 Traffic separation scheme, traffic separated by separation zone

8 Traffic separation scheme, traffic separated by natural obstructions

8 Traffic separation scheme, with outer separation zone, separating traffic using scheme from traffic not using it

G Traffic separation scheme, roundabout

@ Traffic separation scheme, with "crossing gates"

@ Traffic separation schemes crossing, without designated precautionary area

@ Precautionary area

@ Inshore traffic zone, with defined end-limits

§ Inshore traffic zone without defined end-limits

€V Recommended direction of traffic flow, between Traffic separation schemes

§ Recommended direction of traffic flow, for ships not needing a deep water route

§ Deep water route, as part of one-way traffic lane

@ Deep water route, centerline as recommended One-way or Two-way track

8 Recommended route (often marked by centerline buoys.)

§ Two-way route with one-way sections

€V Area to be avoided, around navigational aid

§ Area to be avoided, because of danger of stranding


An inshore traffic zone is a routingmeasure comprising a designated areabetween the landward boundary of aTSS and the adjacent coast, not nor-mally to be used by through traffic (al-though under Rule 10 it may always beused by vessels under 20 meters inlength and sailing vessels) and wherespecial rules may apply. An inshoretraffic zone must be explicitly desig-nated, it is not simply the area be-tween the boundary of the TSS and theland. It is labeled, �INSHORE TRAF-FIC ZONE,� in magenta italics. It mayhave defined endpoints; if so, these aredesignated by T-shaped dashed ma-genta lines (identical to those used todepict a restricted area). Reference tofigure 7�6 indicates that there is no in-shore traffic zone established for thisTSS, because there is no label �IN-SHORE TRAFFIC ZONE� included inthe chart excerpt. (In fact, as of thiswriting, no inshore traffic zones havebeen established in U.S. waters.)

An area to be avoided is an area whichis not recommended for navigation be-cause of shoal hydrography, obstruc-tions, or local and federal regulations.These areas are denoted with a uniquesymbol (M 29.1, M 29.2). For example(IMO), off the coasts of the UnitedStates there are areas to be avoided inthe vicinity of the Louisiana OffshoreOil Port (safety concerns near the plat-form pumping complex and single pointmooring buoys), in the region of Nan-tucket Shoals (because of the greatdanger of strandings and for environ-mental protection), in the region of theNorthwest Hawaiian (Sandwich) Is-lands (to avoid the risk of pollution in adesignated wildlife refuge), off the Cali-fornia coast near the Channel IslandsNational Marine Sanctuary (pollutionconcerns), and throughout the FloridaKeys (to avoid risk of pollution and

damage to the environment).

Calling-in points, requiring participatingvessels to report to a traffic control cen-ter, have been established in certain wa-terways and port approaches (e.g., theNew York Vessel Traffic Service, theBerwick Bay Vessel Traffic Service, etc.)to assist in traffic control. (Refer to theappropriate rules and regulations pub-lished in the CFR for details.) Where es-tablished, calling-in (reporting) pointsare denoted on the nautical chart by aunique magenta symbol (M 40) consist-ing of a circle enclosing an alphanumericdesignator with one or two arrowheadsattached. The alphanumeric designatorcorresponds to a calling-in point givenin the CFR. (Generally numeric or al-phanumeric designators indicate man-datory calling-in points, while alpha-betic designators depict voluntary call-ing-in points.) The arrowhead(s) indicatethat position reports are required forvessels bound in one or two directions.Whenever numeric or alphanumeric des-ignators are charted, the following noteis added in light magenta type:

�Vessel Traffic Services calling-inpoint with numbers; arrow indi-cates direction of vessel movement.�

Pilot boarding areas denote meeting orboarding places where vessels pick upor disembark pilots. (Discussions onpilotage regulations can be found inthe Coast Pilot Manual, appendix B,and in the CFR.) The limits of pilot ar-eas are usually charted with a 2.5 mmmagenta-screened band, or a magentasymbol (T 1.1) if the chart scale is toosmall to show the area. These areas arelabeled �PILOT BOARDING AREA,�or (as shown in figure 7�6), �PILOT-AGE AREA,� in magenta italic type. Apilot boarding area is not part of aTSS, but is included in the section be-cause pilot boarding areas are oftenlocated near elements of a TSS.


�NotesAll TSS are described in the applicable

U.S. Coast Pilot. But, as of this writing, notall TSS are described in the CFR. A note isadded on the nautical chart which providesadditional information on any TSS not de-scribed in the CFR. The exact text of the notevaries with the TSS, but the following servesas an illustration.

�NOTE GTRAFFIC SEPARATION SCHEME

One-way traffic lanes overprinted onthis chart are RECOMMENDED for useby all vessels traveling between thepoints involved. They have been de-signed to aid in the prevention of colli-sions at the approaches to major har-bors and along heavily traveled coastalwaters, but are not intended in any wayto supersede or to alter the applicableRules of the Road. Separation zones areintended to separate inbound and out-bound traffic and to be free of ship traf-fic. Separation zones should not be usedexcept for crossing purposes. Whencrossing traffic lanes and separationzones use extreme caution. A Precau-tionary Area has been established atSan Pedro Bay. It is recommended thatvessels proceed with caution in thisarea.�

This note is �customized� as appropriateto each TSS and is removed upon inclusion ofthe TSS in the CFR.

�Additional InformationAdditional information regarding any TSS

or VTS in U.S. waters can be found in the U.S.Coast Pilot. The following excerpt from theU.S. Coast Pilot, for example, provides informa-tion on the TSS shown in figure 7�6:

�Traffic Separation Schemes(Chesapeake Bay Entrance andSmith Point) have been established forthe control of maritime traffic at the en-trance of Chesapeake Bay and off

Smith Point Light (37°52.8�N.,76°11.0�W.). They have been designedto aid in the prevention of collisions,but are not intended in any way to su-persede or alter the applicable Navi-gation Rules. (See Traffic SeparationSchemes, Chapter 1, for additional in-formation.)

�(30) Traffic Separation Scheme(Chesapeake Bay Entrance).�Thescheme provides for inbound outboundtraffic lanes to enter or depart Chesa-peake Bay from the northeastward andfrom the southeastward. (See NOSchart 12221.)

�(31) A precautionary area with a ra-dius of 2 miles is centered on Chesa-peake Bay Entrance Junction LightedGong Buoy CBJ (36°56.1�N., 75°57.5�W.).

�(32) The northeastern inbound/out-bound traffic lanes are separated by aline of four fairway buoys on bearing250°�070°. The outermost buoy in theline is 6.4 miles 313° from ChesapeakeLight and the innermost buoy is 4.5miles 074° from Cape Henry Light.

�(33) The southeastern approach ismarked by Chesapeake Bay SouthernApproach Lighted Whistle Buoy CB (36°49.0�N., 75°45.6�W.). A RACON is on thebuoy. The inbound/outbound trafficlanes are separated by a Deep-WaterRoute marked by lighted buoys onbearings 302° �122° and 317° �137°.The Deep-Water Route is intended fordeep draft vessels and naval aircraftcarriers entering or departing Chesa-peake Bay. A vessel using the Deep-Water Route is advised to announceits intentions on VHF�FM channel 16as it approaches Lighted Whistle BuoyCB on the south end, and LightedGong Buoy CBJ on the north end of theroute. All other vessels approachingthe Chesapeake Bay Traffic SeparationScheme should use the appropriate in-


bound/outbound lanes of the northeast-erly or southeasterly approaches.

�(34) The Coast Guard advises thatupon entering the traffic lanes, all in-bound vessels are encouraged to makea security broadcast on VHF�FM chan-nel 13, announcing the vessel�s name,location, and intentions.

�(35) Exercise extreme cautionwhere the two routes converge offCape Henry. Mariners are also warnedthat vessels may be maneuvering in thepilotage area which extends into thewestern part of the precautionary area.�

Additional material on TSS can also befound in other publications (e.g., IMO).

�Relevance to the MarinerTSS/VTS have been established to promote

the safe and expeditious flow of traffic.Whether voluntary or mandatory, participationby all vessels operating in the vicinity of a TSSis desirable. The introduction of the TSS hasbeen hailed as a significant �breakthrough� inreducing the incidence of collisions. As Cahill(Strandings and Their Causes) noted:

�The most effective way of achieving areduction in ship casualties is throughreduction of the risks to which marinersare exposed. A dramatic and conclusiveexample of the truth of this proposi-tion is before us in the resultsachieved by the introduction of trafficseparation schemes; specifically thatin the Dover Strait. That scheme is ar-guably the most significant contribu-tion to ship safety since the introduc-tion of steam propulsion.�

For a more critical view of VTS specifi-cally, see Young.

Including TSS information on the nauticalchart certainly simplifies compliance with therouting instructions.

However, participating vessels should beaware that some vessels (either because theychoose not to participate or because they fail toread and understand the procedures) will notfollow the charted patterns. When transitingthese, as well as other areas, caution is thewatchword. As noted in one of the standardreference works (Farwell�s):

�Even with up-to-date charts there re-main instances of ships proceeding con-trary to the direction of traffic flow laiddown for traffic separation schemes.Where collisions have occurred, thecourts have been consistent in findingthat, despite the rogue vessel�s contra-vention of International Regulations�the other rules of the collision regula-tions applied in all respects.�

There have been numerous instances ofcollisions with �rogue� vessels in areas withestablished routes (see Cahill, Collisions andTheir Causes, or Holdert and Buzek), but per-haps the most famous was the Andrea Doria-Stockholm collision in 1956 (see Marriott orHoffer).7

�Smaller VesselsIn the days before the �electronic revolu-

tion,� some might have argued that it was achallenge for operators of smaller vessels(e.g., recreational or small fishing vessels) tocomply fully with an established TSS�par-ticularly in areas sufficiently far offshore toprevent visual fixes being taken on land-based objects and/or for a TSS that is notwell marked by aids to navigation (ATONs).Opting for an inshore route might have beenpreferable to attempting to use the laneswithout suitable means for fixing the vessel�sposition.

7This did not involve a TSS per se, but rather ignoring the 1948 Safety of Life at Sea (SOLAS) recom-mendation on traffic separation�a precursor to today�s TSS.


Now, however, it is common for even smallvessels to have LORAN-C or GPS receiverson board. Use of these electronic aids greatlysimplifies compliance with the establishedTSS, regardless of the prevailing visibility.The traffic lanes can be identified by a se-quence of waypoints (defining the center oflinear portions of the lanes), and the �offcourse� alarm feature common to most ofthese receivers can be set so that the operatoris warned if the vessel strays from the chartedtraffic lane.8 Waypoints can also be used tomark calling-in points for a VTS.

Rule 10, paragraph (e) (ii), permits fishingwithin a separation zone of a TSS. The �offcourse� alarm feature of most modern LO-RAN-C or GPS receivers can also be used towarn the operator if the fishing vessel wan-ders out of the designated separation zone.

Some final tips relevant to use of a TSS in-clude:

Expect to find a significant amount oftraffic in a TSS. These lanes concentratetraffic from a wide ocean area, so thattraffic densities can be quite high. Ves-sels should maintain an alert lookout(both visual and with radar if soequipped).

Ensure that your vessel is equippedwith a radio if using a TSS. This en-ables you to communicate with othervessels using the TSS. A radio is es-sential if using a VTS.

Equip your vessel with a radar reflectorif operating in a TSS and your vessel isnot radar conspicuous. Recreationalvessels, in particular, are often difficultto �see� on radar.

A deep-water route is primarily in-tended to be used by deep-draft ships.Vessels not requiring such channeldepths should avoid using these routesto limit traffic congestion.

When feasible, sailing vessels are prob-ably well advised to remain well clearof a TSS. The slow speed and restrictedmaneuverability of a sailing vessel couldcreate a collision hazard.

Read Rule 10 of the InternationalNavigation Rules carefully before at-tempting to use a TSS. A TSS is noplace for the ill-informed or naïvemariner.

Course LinesSome Great Lakes charts show course lines

that are unofficial traffic separation schemedevised by shipping interests for their own ben-efit. These course lines have not been estab-lished by the USCG, nor are regulations pub-lished in the CFR.

These course lines are charted with ablack dashed line on charts with Englishunits and magenta dashed line on metriccharts. In either case, the labels for thecourse lines are shown in magenta. The labelsinclude distance (in statute and nauticalmiles) and bearings along a course. The pointwhere a course changes direction is shownwith a black dashed line to a point of land orobject ashore. The bearing of the line and thedistance offshore of the turning point are in-cluded in a black label along the dashed line.

If course lines are shown, the following sail-ing directions note (in black vertical letters)is included on Great Lakes metric charts withMercator projections:

8It is recommended that the off-course alarm be set up to warn the mariner well before the limits ofthe traffic lane so as to allow an ample margin of safety.


�SAILING DIRECTIONS. Bearings on sailing courses are trueand distances given thereon are instatute miles (St M) and nautical miles(NM) between points of departure.The true bearing between any twopoints on this chart may be deter-mined by connecting the two pointswith a straight line and measuring theangle of the intersection with a merid-ian line.�

This note is included in the group of notesaligned under the chart title.

CoursesCourses, also called tracks, are a feature in-

cluded on some nautical charts. Courses/tracks are usually shown in rivers, bays, andother inshore waters and are intended prima-rily to help mariners avoid shoal depthsrather than to regulate shipping movement.The decision whether or not to follow acharted course is left to the discretion of themariner rather than a matter of regulation�although some courses are charted in connec-tion with a TSS.

Bearings charted along courses are given indegrees and tenths of a degree with respect totrue (not magnetic) north. Reciprocal bearingsare charted along two-way courses.

Distances along courses may also becharted (in statute or nautical miles). Distancesmay also be shown as a series of mileage

�ticks.� These ticks are generally charted (inmagenta) in statute miles at 1-mile or 5-mileintervals depending upon the scale of thechart.

Recommended courses marked by fixed orfloating ATONs (M 3) are charted with a solidblack line. Traffic flow directional arrows maybe inserted at regular intervals along the line.

Recommended courses not marked byATONs (M 4) are charted with a dashed ma-genta line.

An alternate course (M c) is a secondarycourse available to shallower draft vessels.Usually an alternate course will rejoin the rec-ommended course. The alternate course ischarted with a dashed magenta line whetheror not it is marked by ATONs. Arrows are usedto indicate the direction of traffic flow if so rec-ommended.

Concluding CommentsThe material in this chapter is quite de-

tailed. Although nearly all the topics discussedhave regulatory significance, knowledge of thevarious areas, limits, routes, and tracks, andhow these are depicted on the nautical chart isalso very important to the mariner to ensuresafe passage.

A study of collateral information, such asthe CFR or the U.S. Coast Pilot, is particu-larly important with respect to the chartedfeatures discussed in this chapter. Chartedfeatures, for the most part, are there to alertthe mariner to applicable rules and regula-tions and/or potential hazards.

� � � � � � � � � � � � � � � � � � � � � ��The greatest hazard to navigation is a

bored navigator.�

Anonymous, quoted in Schlereth

� � � � � � � � � � � � � � � � � � � � � �


References��: Civil Reservation.

�� : COLREGS.

��: Course Lines.

��: Danger Area.

��: Explosive Economic and FisheryConservation Zones.

��: Pilot Areas.

��: Recreational Areas and Structures.

��: Restricted Area.

��: Safety Fairway.

��: Territorial Sea and ContiguousZone.

��: Traffic Separation Scheme.

International Maritime Organization. Ships�Routeing, Sixth Edition, Updated with1992 Amendments IMO924E, London, UK,1993.

Marriott, J., Disaster at Sea, HippocreneBooks, New York, NY, 1987.

McKenna, R., �VTS Takes on a Life of ItsOwn,� Professional Mariner, Issue No. 3,October/November 1993, pp. 46�50.

Nemeth, D., �Passage Through a MaritimeCrossroads,� Ocean Navigator, Issue No. 42,September/October 1991, pp. 10�16.

Office of the Federal Register, National Ar-chives and Records Administration. 33Code of Federal Regulations, Parts 1 toEnd (3 Volumes), U.S. Government Print-ing Office, Washington, DC, July 1, 1993.

Ryan, T., �Naval Officer RecountsShiphandling Incident,� ProfessionalMariner, Issue No. 8, August/September1994, pp. 10�14.

Schlereth, H., Commonsense Coastal Naviga-tion, W. W. Norton & Company, New York,NY, 1982.

Trimmer, J. W., How to Avoid Huge Ships or

Anon. �Mississippi Collision Placed 1,800 Pas-sengers in Peril,� Professional Mariner,Issue No. 5, February 1994, pp. 44, et seq.

Anon. �VTS Goes Private; New VTS SystemOpens in Los Angeles/Long Beach,� Profes-sional Mariner, Issue No. 7, June/July1994, p. 34.

Bassett, F. E. and R. A. Smith, Farwell�sRules of the Nautical Road, Sixth Edition,Naval Institute Press, Annapolis, MD,1982.

Brannan, L., �New VTIS On-Line at Califor-nia Port,� Commandant�s Bulletin, Issue6�94, COMDTPUB P5720.2, July 1994, p.5.

Cahill, R. A., Collisions and Their Causes,Fairplay Publications, London, UK, 1983.


Cockcroft, A. N. and J. N. F. Lameijer, AGuide to the Collision Avoidance Rules,Third Edition, Stanford Maritime, London,UK, 1982.

Heinl, R. D., Dictionary of Military and Na-val Quotations, Naval Institutes Press, An-napolis, MD, 1966.

Hoffer, W., Saved! The Story of the AndreaDoria�The Greatest Sea Rescue in His-tory, Summit Books, New York, NY, 1979.

Holdert, H. M. C. and F. J. Bozek. CollisionCases�Judgements and Diagrams, Lloydsof London Press, London, UK, 1984.

Human Technology, Inc. Desk Reference Guide:Specifications Unit, Chart and Map, Fea-ture: Anchorage. Report developed forNational Ocean Service, Charting andGeodetic Services, Marine Chart Branch,Under Contract OPM-85-77, McLean, VA,October 1985.

��: Boundary.


I Never Met A Ship I Liked, National Writ-ers Press, Aurora, CO, 1982, pp. 51�60.

U.S. Department of Commerce, Coast andGeodetic Survey. Nautical Chart Manual,Volume One: Policies and Procedures, Sev-enth Edition, Washington, DC, 1992.

U.S. Department of Commerce, National Oce-anic and Atmospheric Administration,National Ocean Service. Coast PilotManual, 5th Edition, Rockville, MD, 1994.

U.S. Department o f Commerce, Nat ionalOceanic and Atmospheric Administra-

tion, National Ocean Service, and De-partment of Defense, National Imageryand Mapping Agency. Chart No. 1United States of America Nautical ChartSymbols Abbreviat ions and Terms,Ninth Edit ion, Washington, DC, Janu-ary 1990.

U.S. Department of Transportation, UnitedStates Coast Guard. Navigation Rules, In-ternational-Inland, Commandant Instruc-tion (COMDTINST) M 16672.2B, Washing-ton, DC, 1990.

Young, W., �What Are Vessel Traffic Services,and What Can They Really Do?,� Naviga-tion, Vol. 41, No. 1, Spring 1994, pp. 31�56.

Appendix A�Glossary A�1

APPENDIX A

Glossary

IntroductionThis appendix is an authoritative source for terms

used in mapping, charting, and geodesy used in thenautical charting program. Terms and definitions areof specific cartographic interest and may be found inthis manual, on individual charts of maps, applicablesource material, or encountered in archival research.

Where possible, contradictory, controversial, in-complete, or duplicative definitions have been excludedfrom this Glossary. Multiple definitions for a singleterm are included where appropriate. Definitions usedin this Glossary have been taken from authoritativegovernment sources, but chiefly from the U.S. Depart-ment of Commerce, Coast and Geodetic Survey, Nau-tical Chart Manual, Seventh (1992) Edition, VolumeTwo: Definitions, Abbreviations, Symbology, andReferences, Washington, DC, 1992. Words set in boldtype, within definitions, are defined elsewhere in thisGlossary.

This appendix is intended to serve both as a basicreference document and tutorial. Although it is truethat the working vocabulary of most mariners is lessextensive than presented here, mariners are encour-aged to become familiar with the contents of this ap-pendix. As the classic text, Mixter's Primer of Navi-gation (Mixter, G.W., edited by McClench, Primer ofNavigation, Fifth Edition, Van Nostrand Reinhold,New York, NY, 1967, p. 143), notes:

�It is not sufficient to partially understand achart. The navigator must train himself tointerpret the meaning of every mark on a chartand to convey every detail he observes alongthe coast or at sea into the symbols and termsused on charts.�

A Strategy for StudyIt is very much easier to learn the many terms in

this Glossary if attention is paid to the logical rela-tionships between or among similar words. For ex-ample, the terms mud, clay, silt, sand, stones, gravel,pebble, shingle, cobble, rock, and boulder are obvi-ously related. Indeed, all are descriptors used in ChartNo. 1 to describe the �nature of the bottom.� In in-creasing order of particle diameter, these are clay(<0.002 mm), silt (0.002 mm to 0.0625 mm), sand(0.625 mm to 2 mm), gravel (2 mm to 4 mm), pebble(4 mm to 64 mm), cobble (64 mm to 256 mm), androck or boulder (>256 mm). Mud is used as a generalterm which includes both clay and silt. Stones are ageneral term, which includes gravel, pebble, and cobble.Shingle consists of an aggregate of stones ranging from16 mm to 256 mm in diameter. Chart No. 1 is a use-ful source for related terms.

It also helps to relate the terms defined in thisGlossary to practical aspects of navigation and/or sea-manship. Think about the relevance of each of theseterms to typical voyages that you might make. Con-tinuing the example given in the above paragraph,terms relating to the nature of the bottom have prac-tical significance for evaluating the suitability of a placeto anchor and/or the type of anchor to deploy if thevessel is equipped with more than one anchor. Thus,for example, silt and gravel generally offer only poorholding power, and clay is often regarded as havinggood holding qualities. A burying anchor is best formud and sand bottoms, whereas a hooking anchor ispreferable for rocky bottoms.

To help group terms, it may be useful to refer tothe various categories provided in Chart No. 1. Forexample, Section F of Chart No. 1, �Ports,� includesmany of the following related terms: breakwater, groin,

NOAA Chart User's ManualA�2

mole, quay, wharf, pier, gridiron, landing, jetty, dock,and slip. Read the definitions in the Glossary, takingcare to note similarities and differences among theseterms. On your next voyage into waters with theseobjects, compare the chart notations with what youobserve.

Authoritative, But Not ExhaustiveAlthough intended to be authoritative, this Glos-

sary is far from a complete listing of terms related to

nautical charts. Space constraints preclude listingevery potentially relevant term�and not even all theterms used in Chart No. 1, or this manual, are in-cluded herein. Continuing with �nature of the bot-tom� descriptors, this Glossary omits such terms asradiolaria, pteropods, polyzoa, cirripedia, and fucus,for example.

Finally, this Glossary omits terms so common,e.g., bell, boat, etc., as to be understood by virtuallyall mariners.

Abandoned. An adjective referring to an artificialfacility no longer being used for its original pur-pose, as in �abandoned mine.� The term may beused with a symbol (e.g., beside an airport symbol,or with a place name, e.g., Elma (Abandoned)).

Abyss. A very deep, unfathomable place. The term isused to refer to a particular deep part of the ocean,or to any part below 300 fathoms.

Accretion. The gradual building up of land over along period of time, solely by the action of the forcesof nature, on a beach by deposition of water or air-borne material. Artificial accretion is a similar build-up of land by deliberate means. Also called aggra-dation.

Adrift. Afloat or unattached to shore or bottom.

Aerial cableway. A transportation device consist-ing of an endless cable supported on towers. Carsattached to the cable are used for moving people ormaterials.

Aeronautical beacon. A visual aid to navigation,displaying flashes of white or colored light or both,used to indicate the location of airports, landmarks,and certain points of the federal airways in moun-tainous terrain and to mark hazards.

Aeronautical light. A luminous or lighted aid tonavigation intended primarily for air navigation.One intended primarily for marine navigation iscalled a �marine light.� Often shortened to �aerolight.�

Aeronautical radiobeacon. A radiobeacon whoseservice is intended primarily for the benefit of air-craft.

Afloat. Floating, as opposed to being aground.

Aground. Touching, resting, or lodged on the bottomof shallow water. The opposite is afloat. When avessel rests on something solid other than the blocksin a drydock or slipway it is said to be aground. Avessel �takes the ground� when the tide leaves itaground for want of sufficient depth of water, a fairlyfrequent occurrence in open docks.

Aid to Navigation (ATON). Buoys, beacons, fog sig-nals, lights, radiobeacons, leading marks, radioposition fixing systems, radars, inertial systems,and generally any charted or otherwise publisheddevice serving the interests of safe navigation. Seealso: Navigational aid.

Airfield. Landing facility for aircraft, usually with-out a passenger terminal. The services offered foraircraft supply and maintenance are substantiallyless than those of an airport (q.v.). Airfields usuallyhave legal limits which are delineated at 1:50,000and larger scale charts.

Airport. Landing facility for aircraft, usually withmore than one runway and with facilities for han-dling passengers and air freight and for servicingaircraft. The legal limits of the airport are usuallydelineated at chart scales of 1:50,000 and larger.

Airstrip. Landing facility for aircraft consisting of asingle runway, which is usually of gravel construc-tion. Airstrips rarely have a boundary fence or adelineated legal limit.

Alternating. A light showing different colors alter-nately, or a continuous steady light, which shows achange of color.


Altitude. (1) The distance of a location above a refer-ence surface. The most usual reference surface issea level. (2) The distance of a location above thephysical surface of the earth.

Anchorage. A place where a vessel anchors or mayanchor. An area set apart for anchored vessels in aharbor. A suitable place for anchoring is shelteredfrom wind and sea, does not interfere with harbortraffic, and has a sea bottom that gives good hold-ing to anchors. The anchorage space allotted to avessel should include a circle with a radius equal tothe combined length of anchor cable and ship. Adepth of 7 to 8 fathoms at low water is usually con-sidered sufficient for ordinary requirements. For ad-ditional types of anchorage, see Chapter 7.

Anchorage chart. A nautical chart showing pre-scribed or recommended anchorages. Such a chartmay be a harbor chart overprinted with a series ofcircles, each indicating an individual anchorage.

Apparent shoreline. This is the seaward limit ofmarine vegetation, such as mangrove, marsh grass,or trees in water that would reasonably appear tothe mariner from a distance to be the fast shore-line. The seaward limit of kelp, low grass in water,and other low-lying vegetation normally do not con-stitute an apparent shoreline.

Approximate contour. A contour substituted for anormal contour whenever there is a question as toits reliability (reliability is defined as being accu-rate within one-half the contour interval).

Approximate position. In charting, a position thatis considered to be less than third-order accuracy,but is generally considered to be within 100 feet ofits correct geographic location. The method of loca-tion may be an indication of the recorded accuracy.

Aqueduct. A conduit or artificial channel for the con-veyance of water, often elevated, especially one forthe conveyance of a large quantity of water thatflows by gravitation.

Archipelago. An area of water studded with manyislands or with a group of islands; also, such a groupof islands.

Arc of visibility. The portion of the horizon overwhich a lighted aid to navigation is visible. The arcof a light sector, designated by its limiting bearingsas observed from seaward.

Area feature. By definition, a feature extending overan area. It is represented on maps by an outline, a

solid or screened color, cross-hatching, a regularpattern of symbols spread over the area, or a com-bination of these.

Areal feature. A topographic feature, such as sand,swamp, vegetation, etc., which extends over an area.It is represented on the published map or chart bya solid or screened color, by a prepared pattern ofsymbols, or by a delimiting line.

Area to be avoided. A routing measure comprisingan area within defined limits in which either navi-gation is particularly hazardous or it is exception-ally important to avoid casualties and which shouldbe avoided by all ships, or certain classes of ship.

Arm of the sea. A narrow portion of the sea projec-tion from the main body. The expression is oftenshortened to �arm.�

Arroyo. The course of an intermittent stream steep-cut in loose earth; a coulee; a steep-walled trenchlikevalley. (Local in Southwest.)

Articulated light. An articulated light is a verticalpipe structure that oscillates around a universalcoupling connected to a sinker. The structure is keptupright by the buoyancy of a submerged floatationchamber. It is designed primarily to mark narrowchannels with greater precision than conventionalbuoys.

Artificial harbor. A harbor where the desirableshelter from wind and sea has been obtained artifi-cially by the building of moles, piers, breakwaters,and jetties. Also applied to harbors created by sink-ing concrete barges, vessels, and the like to form atemporary sheltered anchorage. See also: Naturalharbor.

Artificial island. An island constructed for the pur-pose of mineral or energy development.

Atoll. A coral island or islands, consisting of a belt ofcoral reef surrounding a central lagoon.

Audible aid to navigation. An aid to navigationtransmitting information by sound waves.

Authorities note. The note included on a chart whichgives the names of the federal agencies that havecontributed to the information used in the compila-tion.

Awash. Situated so that the top is intermittentlywashed by waves or tidal action. The term appliesboth to fixed objects such as rocks, and to floatingobjects with their tops flush with or slightly abovethe surface of the water. See also: Rock awash;


Submerged.

Axis. (1) Any line along which measurements are madein determining the coordinates of a point, or anyline from which angles are measured for the samepurpose. An axis usually serves as a line referencesuch that one of the coordinates of a point lying onthe axis is zero. (2) A line with respect to which ageometric figure is symmetrical. (3) Any line aboutwhich a body rotates or revolves. (4) A line con-necting two distinguished points (e.g., the magneticpoles of the earth are joined by the magnetic axis).

Azimuth. A horizontal angle reckoned clockwise fromthe meridian.

Back range. A range observed astern, particularlyone used as guidance for a craft moving away fromthe objects forming the range.

Backshore. That part of a beach which is usuallydry, being reached only by the highest tides, and byextension, a narrow strip of relatively flat coast bor-dering the sea. See also: Foreshore. That zone ofthe shore or beach lying between the foreshore andthe coastline and acted upon by waves only duringsevere storms, especially when combined with ex-ceptionally high water. Also backbeach. It comprisesthe berm or berms.

Bald. A high rounded knob or mountain top, bare offorest. (Local in southern states.)

Bank. (1) An elevation of the seafloor typically locatedon a shelf and over which the depth of water is rela-tively shallow but sufficient for safe surface navi-gation. Reefs or shoals, dangerous to surface navi-gation, may rise above the general depths of a bank.(2) A shallow area of shifting sand, gravel, mud,etc., as a sand bank, mud bank, etc. (3) A ridge ofany material such as earth, rock, snow, etc., or any-thing resembling such a ridge, as a fog bank orcloud bank. (4) The edge of a cut or fill. (5) Themargin of a watercourse. (6) A number of similardevices connected so as to be used as a single de-vice.

Bar. A ridge or mound of sand, gravel, or other un-consolidated material below the high-water level,especially at the mouth of a river or estuary, orlying a short distance from and usually parallel tothe beach, and which may obstruct navigation.

Bare rock. A rock extending above the datum of meanhigh-water. On NOAA charts, bare rock symbolsare used for rocks extending more than 1 foot abovemean high water on the Atlantic coast, and extend-

ing more than 2 feet above the mean high water onthe Pacific coast. See: Rock; Rock awash; Sunkenrock.

Barrier beach. A bar essentially parallel to the shore,the crest of which is above high water.

Barrier island. A detached portion of a barrier beachbetween two inlets.

Barrier lagoon. A bay roughly parallel to the coastand separated from the open ocean by barrier is-lands. Also the body of water encircled by coral is-lands and reefs, in which case it may be called an�atoll lagoon.�

Barrier reef. A coral reef which roughly parallelsland but is some distance offshore, with deeper wa-ter adjacent to the land, as contrasted with a �fring-ing reef� closely attached to the shore. See also:Fringing reef.

Bar scale. A line or series of lines on a chart, subdi-vided and labeled with the distances represented onthe chart. Also called graphic scale. See also: Scale.

Bascule bridge. A single- or double-leaf span, withthe shoreward ends hinged, allowing the span to beelevated vertically.

Basic survey. A hydrographic survey so complete andthorough that it does not need to be supplementedby other surveys and is adequate to supersede, forcharting purposes, all prior hydrographic surveysof the area.

Basin. (1) A depression of the seafloor more or lessequidimension in plan view and of variable extent.(2) An area of water surrounded by quay walls, usu-ally created or enlarged by excavation, large enoughto receive one or more ships for a specific purpose.See also: Graving dock; Nontidal basin; Scour-ing basin; Tidal basin; Turning basin. (3) Anarea of land which drains into a lake or sea througha river and its tributaries. (4) A nearly land-lockedarea of water leading off an inlet, firth, or sound.

Basin, tidal. A basin affected by tides, particularlyone in which water can be kept at a desired level bymeans of a gate.

Bathymetric chart. A topographic map of the oceanfloor, or the bed of a lake.

Bathymetry. The determination of ocean depths. Thegeneral configuration of seafloor as determined byprofile analysis of depth data.


Bay. (General) An indentation of the coast; anembayment; a subordinate adjunct to a larger bodyof water; a body of water between and inside of twoheadlands (according to Geneva Convention). A well-marked indentation whose penetration is in suchproportion to the width of its mouth as to containlandlocked waters and constitute more than a merecurvature of the coast. The area of such an inden-tation must be as large as or larger than the semi-circle whose diameter is a line drawn across themouth of the indentation.

Bay deltas. Deltas formed at the mouths of streamswhich discharge into bays or estuaries. Their ad-vance toward the bay mouths often extinguisheslagoons behind bay bars or completely fills open bays,thus simplifying the shoreline. When the delta formsat the head of the bay, it is a bay-head delta.

Baymouth bar. A bar extending partly or entirelyacross the mouth of a bay.

Bayou. A minor, sluggish waterway or estuarialcreek, generally tidal or with a slow or impercep-tible current, and with its course generally throughlowlands or swamps, tributary to or connecting withother bodies of water. Various specific meaningshave been implied in different parts of the southernUnited States. Sometimes called slough.

Beach. The zone of unconsolidated material that ex-tends landward from the low-water line to the placewhere there is a marked change in material or physi-ographic form, or to the line of permanent vegeta-tion (usually the effective limit of storm waves). Abeach includes foreshore and backshore. The beachalong the margin of the sea may be called a seabeach.

Beach berm. A nearly horizontal part of the beach orbackshore formed by the deposit of material by waveaction. Some beaches have no berms, others haveone or several.

Beach face. The section of the beach normally ex-posed to the action of the wave uprush. The fore-shore of a beach.

Beacon. A lighted or unlighted aid to navigation at-tached to the earth�s surface. (Lights and daybeaconsboth constitute �beacons.�)

Beam compass. A drafting instrument for drawingcircles with a large radius. The point and pen, orpencil tip, are separate units, mounted to slide andclamp on a long bar or �beam� so that the distancebetween them is equal to the desired radius.

Bearing. The horizontal direction of a line of sightbetween two objects on the surface of the earth.

Bed. The ground upon which a body of water rests.The term is usually used with a modifier to indi-cate the type of water body, as river bed or sea bed.See also: Bottom.

Bell buoy. A steel float surmounted by a short skel-eton tower in which the bell is fixed. Most bell buoysare sounded by the motion of the buoy in the sea. Ina few buoys, the bells are struck by compressed gasor electrically operated hammers.

Bench. (1) A level or gently sloping erosion plane in-clined seaward. (2) A nearly horizontal area at aboutthe level of maximum high water on the sea side ofa dike.

Berm. The nearly horizontal portion of a beach orbackshore having an abrupt fall and formed by depo-sition of material by wave action, and marks thelimit of ordinary high tides.

Berth. The place where a vessel lies when tied up oranchored. A place for securing a vessel.

Bifurcation. A division of a channel into twobranches, a fork.

Bifurcation buoy. A buoy which, when viewed froma vessel approaching from the open sea, or in thesame direction as the main stream of flood current,or in the direction established by appropriate au-thority, indicates the place at which a channel di-vides into two. See also: Junction buoy.

Bight. A bend or curve; a bend in a coast forming anopening bay; a small open bay formed by an inden-tation in the coast; a minor feature which affordslittle protection for vessels.

Blue tint curve. A blue tint is shown in the waterareas to the curve, which is considered the dangercurve for vessels expected to use that particularchart.

Bluff. A bold, steep headland or promontory. A high,steep bank or low cliff.

Bluffs and cliffs. A rigorous definition of either abluff or cliff, or a precise distinction between thetwo, is difficult if not impossible. A feature that iscalled a cliff in one area may be called a bluff inanother. However, most references describe a cliffas a near vertical surface composed of rock. Otherpromontories with steep surfaces, but not exhibit-ing both the near vertical face and the rock struc-ture should be called bluffs.

Boat harbors and marinas. Areas of shelteredwater, generally within harbors or ports, set aside


for the use of small craft, usually with moorings,buoys, and, in the case of marinas, berthing facili-ties.

Boathouse. A building at or near a shore for storageof boats.

Bog. A small open marsh which yields under the foot.

Bold coast. A prominent land mass that rises steeplyfrom the sea.

Bollard. A post (usually steel or reinforced concrete)firmly secured on a wharf, quay, etc., for mooringvessels by means of lines extending from the vesseland secured to the post.

Boom. A floating barrier of timber used to protect ariver or harbor mouth or to create a harbored areafor storage purposes. Also called log boom.

Border break. A cartographic technique used whenit is required to extend cartographic detail of a mapor chart beyond the neatline into the margin. Thistechnique may eliminate the necessity of produc-ing an additional sheet. Also called blister.

Border of chart. The neatline defining the limits ofthe area charted.

Bore. A very rapid rise of the tide in which the ad-vancing water presents an abrupt front of consider-able height. Bores generally occur in shallow estu-aries where the range of tide is large.

Bottom. The ground under a body of water. The termsbed, floor, and bottom have nearly the same mean-ing, but bed refers more specifically to the wholehollowed area supporting a body of water, floor re-fers to the essentially horizontal surface constitut-ing the principal level of the ground under a body ofwater, and bottom refers to any ground covered withwater.

Bottom characteristics. Designations used on sur-veys and nautical charts to indicate the consistency,color, and classification of the sea bottom. Also callednature or quality or character of the bottom.

Bottom land. Lowland formed by alluvial depositalong a stream or in a lake basin; a flood plain.

Boulder. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1 A detached water-rounded stone more than 256 mm in diameter (i.e.,larger than a person�s head).

Boundary line. A line separating two areas. In spe-cific cases, the word �boundary� is often omitted, asin state line; or the word �line� is omitted, as in

international boundary, county boundary, etc. Theterm boundary line is used to specify boundariesbetween political territories, as in state boundarylines between two states.

Bounding Meridian. A Meridian which is coincidentwith a part of the neatline on a chart.

Bounding parallel. A parallel which is coincidentwith a part of the neatline on a chart.

Bowditch. Popular title for Publication No. 9, Ameri-can Practical Navigator.

Branch. A creek or brook, as used locally in southernstates. Also used to designate one of the bifurca-tions of a stream, as a fork.

Breaker. A wave breaking on the shore, over a reef,etc. Breakers may be roughly classified into threekinds, although the categories may overlap: (1) spill-ing breakers break gradually over a considerabledistance, (2) plunging breakers tend to curl overand break with a crash, and (3) surging breakerspeak up, but then instead of spilling or plungingthey surge up on the beach face.

Breakwater. A breakwater is a device protecting ashore area, harbor, anchorage, or basin from waves.A floating breakwater is a contrivance consisting offloating materials connected by mooring chains orcables attached to anchors or stone blocks in such amanner as to form a basin within which vesselsmay be protected from the violence of the waves. Abreakwater may be attached to or separated fromthe shore. See also: Jetty.

Bridge. The term �bridge� means a lawful bridge overnavigable waters of the United States, includingapproaches, fenders, and appurtenances thereto,which are used and operated for the purpose of car-rying railroad traffic, or both railroad and highwaytraffic.

Brook. A stream of less length and volume than acreek, as used locally in the Northeast. Generally,one of the smallest branches or ultimate ramifica-tions of a drainage system.

Buildings. Buildings exist in all sizes and shapes andexhibit various degrees of prominence. Those withtrue landmark value are discussed under Land-mark. Many others, however, are sufficientlyprominent so as to aid the mariner in becomingoriented, especially in harbor areas. These are build-ings such as large warehouses, factories, mainte-nance facilities, etc., that will aid the mariner, forexample, in identifying a particular berth.


Built-up area. An area where the buildings are soclose together that for cartographic clarity a tint orhatching is used to indicate the extent of the area.Landmark buildings are usually depicted within thearea. Cartographic agencies usually define by scalethe extent of congestion required before the areatint or hatching is used, as well as the minimumdimensions of such areas or of clear areas withintinted or hatched areas.

Bulk cargo. Usually a homogeneous cargo stowed inbulk (i.e., loose in the hold and not enclosed in anycontainer such as boxes, bales, bags, etc.). Bulkcargos may be free-flowing articles (such as oil,grain, or ore) which can be pumped or run througha chute or handled by dumping, or articles that re-quire mechanical handling (such as coke, bricks,or pig iron).

Bulkhead. A structure or partition to retain or pre-vent sliding of the land. A secondary purpose is toprotect the upland against damage from wave ac-tion. Bulkheads are frequently filled behind, therebyincreasing the utility of the adjacent land area.

Buoy. A floating object, other than a lightship, mooredor anchored to the bottom, and an aid to naviga-tion.

Buoyage. A system of buoys. One in which the buoysare assigned shape, color, and number distinctionin accordance with location relative to the nearestobstruction is called a cardinal system. One in whichbuoys are assigned shape, color, and number dis-tinction as a means of indicating navigable watersis called a lateral system. See also: IALA Mari-time Buoyage System.

Butte. A lone hill, especially one with steep or pre-cipitous sides.

Cairn. A mound of rough stones or concrete, particu-larly one serving or intended to serve as a land-mark. The stones are customarily piled in a pyra-midal or beehive shape.

Caisson. A watertight gate for a lock, basin, etc. Asteel structure which either floats or slides into placeto close the entrance to a dry dock, lock, or nontidalbasin.

Call letters. Identifying letters, sometimes includ-ing numerals, assigned by competent authority toa radio station. In the United States such identifi-cation is assigned by the Federal CommunicationsCommission (FCC).

Canal. (1) An artificial waterway for navigation. (2)A long, fairly straight natural channel with steep

sloping sides. (3) Any watercourse or channel. (4)A sluggish coastal stream, as used locally on theAtlantic coast of the United States.

Can buoy. An unlighted buoy of which the upper partof the body (above the waterline), or the larger partof the superstructure, has the shape of a cylinderor nearly so. Also called cylindrical buoy.

Canyon. On the seafloor, a relatively narrow, deepdepression with steep sides, the bottom of whichgenerally has a continuous slope.

Cape. A relative extensive land area jutting seawardfrom a continent, or large island, which prominentlymarks a change in or interrupts notably the coastaltrend.

Captain of the Port. The officer of the U.S. CoastGuard, under the command of a District Com-mander, so designated by the Commandant for thepurpose of giving immediate direction to U.S. CoastGuard law enforcement activities within his as-signed area.

Cardinal point. Any of the four principal directions;north, east, south, or west. Directions midway be-tween cardinal points are called intercardinal points.

Cardinal system. A buoyage system generally usedto indicate dangers where the coast is flanked bynumerous islands, rocks, and shoals as well as toindicate dangers in the open sea. In this system thebearing (true) of the mark from the danger is indi-cated to the nearest cardinal point.

Carse. A low, fertile river bottom. (Scottish origin.)

Cartographer. One who practices cartography, par-ticularly a member of the profession regularly con-cerned with any stage in the evaluation, compila-tion, design, or drafting of a map or chart.

Cartographic feature. A term applied to the natu-ral or cultural items shown on a map or chart. Thethree main categories are: �point feature,� �line fea-ture,� and �area feature.�

Cartographic license. The freedom to modify manu-script information in order to improve the clarity ofthe chart or map.

Cartography. The art, science, and technology ofmaking charts or maps, together with their studyas scientific documents and works of art. In thiscontext, maps may be regarded as including alltypes of maps, plans, charts and sections, three-dimensional models and globes representing theearth or any celestial body at any scale.


Cascade. A fall of water over steeply sloping rocks,usually comparatively small or one of a series.

Cataract. A waterfall, usually larger than a cascade,over a precipice.

Catwalk. See: Fore-and-aft bridge.

Causeway. A raised way, as for a road, across wetground, or water. A causeway is a raised roadwayof solid structure built primarily to provide a routeacross wet ground or an intertidal area.

Cautionary characteristic. Of a light, a uniquecharacteristic which can be recognized as impart-ing a special cautionary significance (e.g., a quickflashing characteristic phase indicating a sharp turnin a channel).

Cavern. A large, natural, underground cave or seriesof caves. Often, but not always, used to imply large-ness or indefinite extent to distinguish from �cave.�

Cay (also kay, key). A low, flat island of sand, coral,etc., awash or drying at low water; a term origi-nally applied to the coral islets around the coastand islands of Caribbean Sea.

Ceja. The cliff at a mesa edge; an escarpment. Localin Southwest.

Central meridian. The line of longitude at the cen-ter of a map or chart projection. Generally, the ba-sis for constructing the projection.

Centerline controlling depth. The controllingdepth of a waterway, which applies only to the cen-ter of the waterway; it is usually the result of areconnaissance-type survey consisting of only a fewlines of soundings which do not provide adequatecoverage to determine the controlling depth of theentire waterway.

Cerrito (or cerrillo). A small hill. (Local in South-west.)

Cerro. Hill, highland; ridge. (Local in Southwest.)

Chain. A group of associated stations of aradionavigation system. A LORAN-C chain consistsof a master station and two or more secondary sta-tions.

Chalk. One of several descriptors of the �nature of theseabed� used in Chart No. 1 Chalk is soft earthysandstone of marine origin, composed chiefly ofminute shells. It is white, gray, or buff in color.Part of the ocean bed and shores and composed ofchalk, notably the �white cliffs of Dover,� England.Chalk exhibits variable, but sometimes poor, hold-ing qualities.

Channel. (1) That part of a body of water deep enoughfor navigation through an area otherwise not suit-able. It is usually marked by a single- or double-line of buoys and sometimes by ranges. (2) Thedeepest part of a stream, bay, or strait, throughwhich the main current flows. (3) A name given tocertain large straits, as the English Channel. (4) Ahollow bed through which water does or may run.(5) A band of radio frequencies within which a ra-dio station must maintain its modulated carrier fre-quency to prevent interference with stations on ad-jacent channels. Also called frequency channel.

Channel, sea. A long, narrow, U-shaped or V-shapedshallow depression of the seafloor, usually occur-ring on a gently sloping plain or fan.

Characteristic. (1) The color and shape of a daymarkor buoy or the color and period of light used for iden-tifying the aid. (2) The identifying signal transmit-ted by a radiobeacon.

Characteristic color. Of a light, the unique identi-fying color (e.g., in the U.S. buoyage system, greenlights are used only on black buoys or on horizon-tally banded black-and-red buoys with the topmostband black).

Characteristics of light. All particularities of a light,such as color, period, group number, visibility,height above sea level, and character. Also calledlight characteristics.

Characteristic phase. Of a light, the sequence andlength of light and dark periods by which a naviga-tional light is identified (i.e., whether fixed, flash-ing, interrupted, quick flashing, etc.).

Chart agent. Business establishments that are un-der contract with NOAA and that receive discountsfor resale of nautical and aeronautical navigationalcharts and related publications to the general pub-lic at retail prices stipulated by NOAA.

Chart, bathymetric. A topographic map of the bedof the ocean.

Chart datum. The datum to which soundings on achart are referred. It is usually taken to correspondto a low-water elevation.

Charted visibility. The extreme distance, shown innumbers on a chart, at which a navigational lightcan be seen. This may be the geographic range whenlimited by the curvature of the earth and the heightsof the light and the observer or the luminous rangewhen limited only by the intensity of the light, clear-ness of the atmosphere, and sensitivity of theobserver�s eyes.


Chart, isogonic. Chart showing magnetic declina-tion with isogonic lines and the annual rate ofchange in declination with isoporic lines.

Chartlet. A corrected reproduction of a small area ofa nautical chart which is pasted to the chart forwhich it is issued. These chartlets are disseminatedin Notice to Mariners when the corrections are toonumerous or of such detail as not to be feasible inprinted form. (Also called: block, block correction,chart amendment patch.)

Chart, Mercator. A chart on the Mercator projec-tion. This is the chart commonly used for marinenavigation. In Mercator Chart, a rhumb line is astraight line.

Chart, nautical. A chart specifically designed to meetthe requirements of marine navigation, showingdepths of water, nature of bottom, elevations, con-figuration and characteristics of coast, dangers andaids to navigation. (Also called: marine chart, hy-drographic chart, or simply chart.)

Chart scale. The ratio between a distance on a chartand the corresponding distance represented, as1:80,000 (natural scale), or 30 miles to an inch (nu-merical scale). May be called map scale when ap-plied to any map. See also: Representative frac-tion.

Chart sounding datum. The tidal datum to whichsoundings and drying heights on a chart are re-ferred. It is usually taken to correspond to a low-water stage of the tide. Often shortened to �chartdatum,� especially when it is clear that reference isnot being made to a horizontal datum.

Chasm. A deep breach in the earth�s surface; an abyss;a gorge; a deep canyon.

Chimney. A label on a nautical chart which indicatesa relatively small, upright structure projectingabove a building for the conveyance of smoke.

Circle, great. The circle formed by the intersectionof a sphere with a plane that passes through thecenter of the sphere. The shortest distance betweenany two points on a sphere is along the arc of agreat circle connecting the two points.

Circle of visibility. That circle surrounding an aidto navigation and in which the aid is visible.

Clay. One of several descriptors of the �nature of theseabed� used in Chart No. 1. See under: Mud.

Clearance, bridge. Minimum vertical or horizontalspace available for passage.

Cliff. Land arising abruptly for a considerable dis-tance above water or surrounding land. See also:Bluff.

Closed. A manned aid temporarily discontinued forthe winter season.

Closing line. The dividing line between inland wa-ters and the marginal sea across the entrance of atrue bay. See also: Marginal sea.

Coast. The part of the land next to the sea. This termincludes natural appendages of the territory whichrise out of the water, although they may not be ofsufficient firmness to be inhabited or fortified. Shoalsperpetually covered with water are not includedunder the term �coast.� Coast is the term used withreference to the land, while �shore� is the term usedwith reference to the sea.

Coast charts. These NOAA charts are published atscales from 1:50,000 to 1:150,000 and are intendedfor nearshore navigation inside outlying reefs andshoals, in entering or leaving bays and harbors ofconsiderable size, and in navigating the larger in-land waterways.

Coastal confluence zone. A coastal area of theUnited States which has an outer boundary of 50nautical miles from shore or the 100-fathom curve,whichever is farther, and an inner boundary of theshoreline or the outer boundary of the harbor en-trance, whichever is farther.

Coastal plain. Any plain which has its margin onthe shore of a large body of water, particularly thesea, and generally represents a strip of geologicallyrecent emerged sea bottom.

Coastal waters. (1) The U.S. waters of the GreatLakes (Erie, Huron, Michigan, Ontario, and Supe-rior); (2) the territorial seas of the United States;and (3) those waters directly connected to the GreatLakes and territorial seas (i.e., bays, sounds, har-bors, rivers, inlets, etc.), where any entrance ex-ceeds 2-nautical miles between opposite shorelinesto the first point where the largest distance betweenshorelines narrow to 2 miles as shown on the cur-rent edition of the appropriate NOAA chart usedfor navigation.

Coasting. Proceeding approximately parallel to acoastline (headland to headland) in sight of land, orsufficiently often in sight of land to fix the ship�sposition by observations of land features.

Coastline. Generally, where the shore directly con-tacts the open sea, the line on the shore reached by


the ordinary low tides comprised the coastline fromwhich the distance of three geographic miles ismeasured. The line has significance for both domes-tic and international law (in which it is termed the�baseline�), and is subject to precise definitions.Special problems arise when offshore rocks, islands,or other bodies exist, and the line may have to bedrawn to seaward of such bodies.

Coastwise navigation. Navigation in the vicinityof a coast, in contrast with offshore navigation at adistance from a coast. See also: Coasting.

Cobble. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1 See under: Stones.

COLREGS. Acronym for International Regulationsfor Preventing Collisions at Sea. Lines of demarca-tion delineating those waters upon which marinersmust comply with the International Regulations forPreventing Collisions at Sea, 1972 (72 COLREGS)and those waters upon which mariners must com-ply with the Navigation Rules for Harbors, Rivers,and Inland Waters (Inland Rules). The waters out-side the lines are COLREGS waters. For specificsconcerning COLREGS demarcation lines see: U.S.Code of Federal Regulations (CFR), Title 33, Navi-gation and Navigable Waters; Part 82, COLREGSdemarcation lines.

Commissioned. An aid previously reported closed orwithdrawn which has been placed in operation.

Compass course. (1) Course relative to compassnorth. (2) Compass direction. Horizontal directionexpressed as angular distance from compass north.

Compass direction. Direction as indicted by com-pass without any allowances for compass error. Thedirection indicated by a compass may differ by aconsiderable amount from true or magnetic direc-tion.

Compass, gyroscopic. A compass consisting of agyroscope suspended so that its axis of rotationpoints north.

Compass, magnetic. A device that indicates direc-tion by means of a magnet supported at its mid-point so that the magnet aligns itself with the localmagnetic field. The end of the magnet, which pointsin the general direction of north, is marked.

Compass north. The uncorrected direction indicatedby the north-seeking end of a compass needle. Seealso: Magnetic north.

Compass rose. A circle graduated in degrees, clock-

wise from 0° at the reference direction to 360°. Com-pass roses are placed at convenient locations on theMercator chart or plotting sheet to facilitate mea-surement of direction.

Compilation. (1) The production of a new or revisedmap or chart, or portions thereof, from existingmaps, aerial photographs, surveys, new data, andother sources. (2) The production of a map or chart,or portions thereof, from aerial photographs andgeodetic control data, by means of photogrammet-ric instruments.

Containerized cargo. Cargo which is carried insealed, specially constructed containers. In roll-on/roll-off container operations, truck trailers, com-plete with chassis and wheels, are rolled onto andoff of special types of ships or barges by means oframps. In lift-on/lift-off operations, containers areloaded and unloaded by means of high-speed ship-board or shore-based cranes.

Conterminous United States. Comprises the 48states of the United States and the District of Co-lumbia; all of the states exclusive of Alaska andHawaii. They have common boundaries and are notseparated by foreign territory or the high seas.

Continental borderland. A province adjacent to acontinent, normally occupied by or bordering a con-tinental shelf, that is highly irregular with depthswell in excess of those typical of a continental shelf.

Continental margin. The zone, generally consist-ing of shelf, slope, and rise, separating the conti-nent from the abyssal plain or deep sea bottom.

Continental rise. A gentle slope rising from the oce-anic depths toward the foot of a continental slope.

Continental shelf. The submerged portion of a con-tinent, which slopes gently seaward from the low-water line to a point where a substantial break ingrade occurs, at which point the bottom slopes sea-ward at a considerable increase in slope until thegreat ocean depths are reached. The point of breakdefines the edge of the shelf, and the steeper slop-ing bottom the continental slope. Conventionally,the edge is taken at 100 fathoms (200 meters) butinstances are known where the increase in slopeoccurs at more than 200 or less than 65 fathoms.

Contour. A line joining points of equal vertical dis-tance above or below a datum. Such a line on a mapis a type of Isoline.

Contour line. A line connecting points of equal el-


evation or equal depth. One connecting point of equaldepth is usually called a fathom curve, or fathomline. See also: Form line.

Controlling depth. (1) The least depth in the ap-proach or channel to an area, such as a port or an-chorage, governing the maximum draft of vesselsthat can enter. (2) The least depth within the lim-its of a channel; it restricts the safe use of the chan-nel to drafts of less than that depth. The centerlinecontrolling depth of a channel applies only to thechannel centerline; lesser depths may exist in theremainder of the channel. The mid-channel control-ling depth of a channel is the controlling depth ofonly the middle half of the channel. See also: Fed-eral project depth.

Conventional nautical charts. These charts areflat, printed reproductions published by NOAA ofsome portion of the navigational part of the earth�ssurface. Depending on their scale, these charts showthe nature and shape of the coast, depth of the wa-ter, general configuration and character of the bot-tom, prominent landmarks, port facilities, culturaldetails, dredged channels, aids to navigation, ma-rine hazards, magnetic variations, and seawardboundaries. Changes brought about by people andnature require that nautical charts be constantlymaintained to aid safe navigation.

Coordinates. Linear or angular quantities, whichdesignate the position of a point in relation to a givenreference system.

Coral. In the strict sense, coral is a bottom-dwellingmarine organism, which secretes an external skel-eton of calcium carbonate and which frequentlyforms large, irregular colonies with numerous coralheads and pinnacle. In reality, coral formations areusually a mixture of coral and other marine organ-isms along with other debris and chemically pre-cipitated rock. For shoreline mapping purposes, arock or coral formation is a naturally occurring,consolidated rock, or coral mass, that differs con-spicuously from adjacent objects and materials, andwhich is too large to be adequately represented onthe shoreline map by a single rock (coral) symbol.

Coral head. A massive mushroom or pillar-shapedcoral growth.

Coral reef. A reef made up of coral, fragments of coraland other organisms, and the limestone resultingfrom their consolidation.

Correction of soundings. The adjustment of sound-ings for any departure from true depth because ofthe method of sounding or any fault in the measur-

ing apparatus.

Coulee. A steep-walled, trenchlike valley; a wash,gulch, or arroyo through which water flows inter-mittently. (Western United States.)

Course. The intended horizontal direction of travel.It is measured from 0° at the reference directionclockwise through 360°; strictly for marine naviga-tion, the term applies to the direction to be steered,which sometimes differs from the direction intendedto be made good over the ground. The course is des-ignated as true, magnetic, or compass, as the refer-ence direction is true, magnetic, or compass northrespectively.

Course, recommended. A line shown on a chart,which has been specially examined to ensure thatit is free of dangers, and along which ships are ad-vised to navigate. Also called recommended track.

Cove. A small, sheltered recess in a coast, often in-side a larger embayment.

Covers and uncovers (or discovers). Expressionintended to indicate an area of a reef or other pro-jection from the bottom of a body of water, whichperiodically extends above and is submerged belowthe surface. Also referred to as dries or uncovers.

Crag. A steep, rugged rock; a rough, broken cliff of aprojecting point of rock; also a detached fragmentof a rock.

Crater. The bowl-shaped depression around the ventof a volcano or a geyser; also a hole formed by theimpact of a meteorite, the detonation of a mine, orthe like.

Creek. (1) A stream of less volume than a river, butlarger than a brook. (2) A small tidal channelthrough a coastal marsh. (3) A wide arm of a riveror bay.

Crest. The summit land of any eminence; the high-est natural projection which crowns a hill or moun-tain, from which the surface dips downward in op-posite directions.

Crevasse. A deep crevice, or fissure, especially in aglacier. A break in a levee or other stream embank-ment.

Crib. A permanent marine structure, usually designedto support or elevate pipelines; especially a struc-ture enclosing a screening device at the offshore endof a potable water intake pipe. The structure is com-monly a heavy timber enclosure that has beensunken with rocks or other debris.


Culture. Artificial features that are under, on, andabove ground, which are delineated on a chart ormap. These features include roads, trails, buildings,canals, sewer systems, and boundary lines. In abroad sense, the term also applies to all names, otheridentification, and legends on a chart or map.

Cupola. A label on a nautical chart which indicates asmall dome-shaped tower or turret rising from abuilding.

Current. Generally, a horizontal movement of wa-ter. Currents may be classified as tidal and nontidal.

Cut-off. A new, and relatively short, channel formedwhen a stream cuts through the neck of an oxbowor horseshoe bend. An artificial straightening orshort cut in a channel.

Dalles. The nearly vertical walls of a canyon or gorge,usually containing a rapid. (Local in Northwest.)

Danger area. The specified area above, below, orwithin which there may exist potential danger. Seealso: Prohibited area; Restricted area.

Danger line. (1) A line drawn on a chart to indicatethe limits of safe navigation for a vessel of specificdraft. (2) A line used to draw the navigator�s atten-tion to a danger, which would not stand out clearlyenough if it were represented on the chart solely bythe specific symbols.

Danger sounding. A minimum sounding chosen fora vessel of specific draft in a given area to indicatethe limit of safe navigation.

Dangerous cargo. The term �dangerous cargo�means all explosives and other hazardous materi-als or cargo covered by federal regulations.

Dangerous rock. A sunken rock of a small area (pin-nacle), at such a depth as to be considered danger-ous to surface navigation.

Dangerous wreck. A wreck submerged at such adepth as to be considered dangerous to surface navi-gation.

Datum, geodetic. A set of constants specifying thecoordinate system used for geodetic control, i.e., forcalculating coordinates of points on the earth.

Datum plane. A surface used as a reference fromwhich heights or depths are reckoned. The plane iscalled a tidal datum when defined by a phase of thetide, for example, high water or low water.

Datum sounding. The horizontal plane or tidal da-tum to which the soundings on a hydrographic sur-

vey are reduced. Also called datum for soundingreduction.

Datum, tidal. A surface with a designated elevationfrom which heights or depths are reckoned, definedby a certain phase of the tide.

Datum, vertical. For marine applications, a baseelevation used as a reference from which to reckonheights or depths.

Daybeacon. An unlighted fixed structure which isequipped with a daymark for daytime identification.

Deadhead. A submerged or barely awash log or treetrunk freely floating at varying attitudes in con-trast to the plane formed by the still (undisturbed)surface of the water. At times, one end of a dead-head may become attached to the bottom with theopposite (unattached) end floating.

Dead reckoning. The process of determining the po-sition of a vessel at any instant by applying to thelast well-determined position (point of departure orsubsequent fix) the run that has since been made.The position so obtained is called a dead reckoningposition. When the principle purpose of dead reck-oning is to lay down on the chart a reference plotfor evaluating the reasonableness of positioning byother means, the dead reckoning plot is usually con-structed without allowance for disturbing elements(such as current, wind, sea conditions, roughnessof vessel�s bottom, etc.), the course steered beingused for direction and ordered speed being used forrate of movement along the course line.

Deep. A relatively small area of exceptional depthfound in a depression. The term is generally re-stricted to depths greater than 3,000 fathoms.

Deep-draught route. A route which is primarilyselected for use by ships which, because of theirdeep draught, may not be able to navigate safelyoutside such route.

Deep-water route. A route in a designated areawithin definite limits which has been accuratelysurveyed for clearance of sea bottom and submergedobstacles to a minimum indicated depth of water.

Defense Mapping Agency. The DMA (renamed Na-tional Imagery and Mapping Agency in 1995) wasestablished as an agency of the Department of De-fense (DOD) on January 1, 1972, under the provi-sions of the National Security Act of 1947, asamended (61 Stat. 495; 50 U.S.C. 401). The mis-sion of the DMA is to provide mapping, charting,and geodetic support and services to the Secretaryof Defense, the Joint Chiefs of Staff, the military


departments, and other DOD components throughthe production and worldwide distribution of maps,charts, precise positioning data, and digital datafor strategic and tactical military operations andweapons systems.

Degaussing. Neutralization of the strength of themagnetic field of a vessel, by means of suitably ar-ranged electric coils permanently installed in thevessel. See also: Deperming.

Degaussing range. An area for determining mag-netic signatures of ships and other marine craft.Such signatures are used to determine requireddegaussing coil current settings and other requiredcorrective action. Sensing instruments and cablesare installed on the sea bed in the range, and thereare cables leading from the range to a control posi-tion ashore. The range is usually marked by dis-tinctive buoys.

Delta. The low alluvial land, deposited in a more orless triangular form at the mouth of a river, whichis often cut by several distributaries of the mainstream.

Density of soundings. Intervals between lines ofsounding and soundings in the same line. Densityof soundings mostly depends on the scale and na-ture of the survey. Also called frequency of sound-ings.

Deperming. The process of changing the magneticcondition of a vessel by wrapping a large conductoraround it a number of times in a vertical plane,athwartships, and energizing the coil thus formed.If a single coil is placed horizontally around the ves-sel and energized, the process is called flashing ifthe coil remains stationary, and wiping if it is movedup and down. See also: Degaussing.

Depression. A general term signifying any depressedor lower area in the ocean floor; a hollow completelysurrounded by higher ground and having no natu-ral outlet for surface drainage.

Depression contour. A closed contour delimiting anarea of lower elevation than the surrounding ter-rain. Directional ticks extend from the contour in adownhill direction.

Depth. The vertical distance from a given water levelto the bottom. The charted depth is the vertical dis-tance from the tidal datum to the bottom. The leastdepth in the approach or channel to an area, suchas a port or anchorage, governing the maximumdraft of vessels that can enter is called the control-ling depth.

Depth contour navigation. A method of positiondetermination by utilizing the depth contours onthe nautical chart. Consists in fitting a series ofobserved echo soundings to the depth contours byrecording a number of soundings and simultaneouslog distances and plotting them on a strip of trans-parent paper at the scale of the chart. The line ofsoundings is fitted to the depth contours by movingit so that it remains parallel to the true coursesteered.

Depth, controlling. The least depth in the approachor channel to an area, such as a port of anchorage,governing the maximum draft of vessels that canenter.

Depth curve. A depth curve is a line connectingpoints of equal water depth which is sometimes sig-nificantly displaced outside of soundings, symbols,and other chart details for clarity as well as gener-alization. Depth curves therefore often represent anapproximate location of the line of equal depth asrelated to the surveyed line delineated on the source.

Depth finder. An instrument for the measurementof the depth of water, particularly an echo sounder.

Derelict. Any property abandoned at sea, often ofsufficient size as to constitute a menace to naviga-tion; especially an abandoned vessel. See also:Wreck.

Deviation. The angle between the magnetic merid-ian and the axis of a compass card, expressed indegrees east or west to indicate the direction inwhich the northern end of the compass card is off-set from magnetic north. Deviation is caused bydisturbing magnetic influences in the immediatevicinity of the compass, as within the craft.

Deviation table. A table of the deviation of a mag-netic compass on various headings, magnetic orcompass.

Diaphone. A sound signal emitter operating on theprinciple of periodic release of compressed air con-trolled by the reciprocating motion of a piston oper-ated by compressed air. The diaphone usually omitsa powerful sound of low pitch which often concludeswith a brief sound of lower pitch called the grunt.The emitted signal of a two-toned diaphone consistsof two tones of different pitch, in which case thesecond tone is of lower pitch.

Diaphragm horn. A sound signal emitter compris-ing a resonant horn excited at its throat by impul-sive emissions of compressed air regulated by anelastic diaphragm. Duplex or triplex horn units of


different pitch produce a chime signal. Also calledcompressed air horn.

Dike. A bank of earth or stone used to form a barrier,frequently and confusingly interchanged withLevee, definition 1. A dike restrains water withinan area that is normally flooded.

Directional light. A light illuminating a sector orvery narrow angle and intended to mark a direc-tion to be followed.

Discharge. Includes, but is not limited to, any spill-ing, leaking, pouring, pumping, emitting, empty-ing, or dumping.

Discolored water. Unnatural colored areas in thesea due to the existence of shoals. Sea water havinga color other than the blues and greens normallyseen. Variations of the colors red, yellow, green, andbrown, as well as black and white, have been re-ported. Discolorations may appear in patches,streaks, or large areas and may be caused by con-centrations of inorganic or organic particles orplankton.

Discontinued. To remove from operating (perma-nently or temporarily) a previously authorized aid.

Discrepancy. Failure of an aid to maintain its posi-tion or function as prescribed in the Light List.

Discrepancy buoy. An easily transportable buoyused to temporarily replace an aid to navigation notwatching properly.

District Commander. The officer of the U.S. CoastGuard designated by the Commandant to commanda U.S. Coast Guard District.

Diurnal. Having a period or cycle of approximatelyone tidal day. Thus, the tide is said to be diurnalwhen only one high water and one low water occurduring a tidal day, and the tidal current is said tobe diurnal when there is a single flood and a singleebb period in the tidal day. A rotary current is diur-nal if it changes its direction through all points ofthe compass once each tidal day.

Divide. The line of separation between drainage sys-tems; the summit of an interfluve. The highest sum-mit or a pass or gap.

Dock. (1) The slip or waterway between two piers, orcut into the land for the berthing of ships. A pier issometimes erroneously called a dock. Also calledslip. See also: Jetty; Landing; Quay; Wharf. (2)A basin or enclosure for reception of vessels, andprovided with means for controlling the water level.A wet dock is one in which water can be maintained

at various levels by closing a gate when the wateris at the desired level. A dry dock is a dock provid-ing support for a ship, and means of removing thewater so that the bottom of the ship or other craftcan be exposed. A dry dock consisting of an artifi-cial basin is called a graving dock; one consisting ofa floating structure is called a floating dock. (3)Used in the plural, a term used to describe area ofthe docks, wharves, basins, quays, etc.

Dock, floating. A form of dry dock consisting of afloating structure of one or more sections which canbe partly submerged by controlled flooding to re-ceive a vessel, then raised by pumping out the wa-ter so that the vessel�s bottom can be exposed.

Dock sill. The foundation at the bottom of the en-trance to a dry dock or lock against which the cais-son or gates close. The depth of water controllingthe use of the dock or lock is measured from the sillto the surface.

Dock, wet. A dock in which water can be maintainedat any level by closing a gate when the water is atthe desired level.

Dog leg. A leg which does not lead directly to the des-tination or way point. It is followed to comply withestablished procedures, avoid possible dangers orbad weather, delay time of arrival, etc.

Dolphin. A mooring post or buffer placed at the en-trance of a dock, alongside a wharf or in the middleof a stream. In the first and second instances it isused as a buffer. In the third it is used as a mooringpost by vessels which discharge their cargoes with-out going alongside a dock or wharf. Each dolphinis generally composed of a series of heavy piles con-tiguous to each other. They are arranged in a circle,brought together and capped over the top.

Dome. A label on a nautical chart which indicates alarge, rounded, hemispherical structure rising froma building or a roof of the same shape. A prominentexample is that of the Capitol of the United Statesin Washington, DC. Also a smoothly rounded, rock-capped mountain summit, roughly resembling thedome or cupola of a building.

Doubtful sounding. Of uncertain depth. The expres-sion, as abbreviated, is used principally on chartsto indicate a position where the depth may be lessthan indicated, the position not being in doubt.

Draft (or draught). The vertical distance, at anysection of a vessel from the surface of the water tothe bottom of the keel. When measured at or nearthe stem, it is referred to as draft forward and when


measured at or near the stern as draft aft. Thesedrafts are more specifically described as displace-ment drafts as opposed to navigational drafts whichare measured to the lowest appendage to the hullas opposed to the keel.

Drag. To tow a line or object below the surface, todetermine the least depth in an area or to insurethat a given area is free from navigational dangersto a certain depth. Drag and sweep have nearly thesame meanings. Drag refers particularly to the lo-cation of obstructions or the determination thatobstructions do not exist. Sweep may include, addi-tionally, the removal of any obstructions located.See also: Sweep.

Drain. A channel; a trench; a watercourse, especiallya narrow one.

Drawbridge. A bridge that can be raised, lowered, ordrawn aside.

Drawing. An impression following the printing of anautical chart of either its black or its magentadetail on matte finish transparent plastic, used inrevising subsequent printings of the chart.

Dredged material. The term �dredge material�means any material excavated or dredged from navi-gable waters of the United States.

Dry dock. An enclosed basin into which a ship is takenfor underwater cleaning and repairing. It is fittedwith watertight entrance gates, which when closedpermit the dock to be pumped dry. In modern drydocks the gates opening in the middle and hingedat sides having been replaced by a caisson or pon-toon that fits closely into the entrance. The caissonis flooded and sunk in place, and can be pumpedout, floated and warped away from the dock entranceto permit passage of vessels. Also called Gravingdock.

Dry harbor. A small harbor which either dries atlow water or has insufficient depths to keep vesselsafloat during all states of the tide. Vessels using itmust be prepared to take the ground on the fallingtide.

Drying heights. Heights above chart sounding da-tum of those features which are periodically cov-ered and exposed by the rise and fall of the tide.

Dry wash. A wash, arroyo, or coulee in the bed ofwhich there is not water, except at infrequent in-tervals and for short periods.

Duck blind. For NOAA charting purposes, a duckblind is a nonfloating structure, used for conceal-

ing waterfowl hunters, usually consisting of awooden framework covered with brush.

Dumping grounds. Although shown on nauticalcharts as dumping grounds in U.S. waters, the fed-eral regulations for these areas have been revokedand their use for dumping discontinued. These ar-eas will continue to be shown on nautical chartsuntil such time as they are no longer considered tobe a danger to navigation. See also: Dump site,Spoil area.

Dump site. An area established by federal regula-tion in which dumping of dredged and fill materialand other nonbuoyant objects is allowed with theissuance of a permit. Dump sites are shown on nau-tical charts. See also: Dumping grounds, Spoilarea.

Dune. A hill or ridge formed by the wind from sand orother granular material.

Ebb. Tidal current moving away from land or down atidal stream. The opposite is Flood. Sometimes theterms �ebb� and �flood� are also used with referenceto vertical tidal movement, but for this verticalmovement the expressions falling tide and risingtide are considered preferable.

Ebb current. The tidal current associated with thedecrease in the height of a tide. Ebb currents gen-erally set seaward.

Ebb tide. The portion of the tide cycle between highwater and the following low water. Also called fall-ing tide.

Echo sounder. An instrument for determining thedepth of water by measuring the time interval be-tween the emission of a sonic or ultrasonic signaland the return of its echo from the bottom. Alsocalled echo sounding instrument (or apparatus),sonic depth finder, or ultrasonic depth finder, asappropriate. See also: Echo sounding.

Echo sounding. A method of measuring the depth ofwater by determining the time required for soundwaves to travel, at a known velocity, from the sur-vey vessel to the bottom and return.

Eclipse. A phase of the characteristic of a flashinglight during which the light is not exhibited.

Eddy. A current of water running contrary to the maincurrent or moving circularly; a whirlpool.

Electronic aid to navigation. An aid to navigationusing electronic equipment. If the navigational in-formation is transmitted by radio waves, the device


may be called a radio aid to navigation.

Electronic navigation. Navigation by means of elec-tronic equipment. The expression electronic navi-gation is more inclusive than radionavigation, sinceit includes navigation involving any electronic de-vice or instrument.

Elevations. Heights of natural and artificial objectsabove an adopted reference plane. On NOAA nauti-cal charts, the elevations of bare rocks, bridges, land-marks, and lights are referenced to the plane ofmean high water; contour and summit elevationsare referenced to mean sea level, if the source forsuch information is referenced to this plane.

Embankment. An artificial deposit of material thatis raised above the natural surface of the land andused to contain, divert, or store water; support roadsor railways; or for other similar purposes.

Embayment. Any indentation of a coast regardlessof width at the entrance or depth of penetration intothe land.

Entrance lock. A lock between the tideway and anenclosed basin when their water levels vary. Bymeans of the lock, which has two sets of gates, ves-sels can pass either way at all states of the tide.Also called Tide lock. See also: Nontidal basin.

Escarpment. An extended line of cliffs or bluffs; ahigh, steep face of rock; an elongated and compara-tively steep slope of the seafloor, separating flat orgently sloping areas.

Establish. To place an authorized aid in operationfor the first time.

Established direction of traffic flow. A traffic flowpattern indicating the directional movement of traf-fic as established within a traffic separation scheme.

Estuary. An embayment of the coast in which freshriver water entering at its head mixes with the rela-tively saline ocean water. When tidal action is thedominant mixing agent it is usually termed a �tidalestuary.� Also, the lower reaches and mouth of ariver emptying directly into the sea where tidalmixing takes place. The later is sometimes called ariver estuary.

Everglade. A tract of swampy land covered mostlywith tall grass; a swamp or inundated tract of lowland. (Local in the South.)

Exclusive Economic Zone. The Exclusive EconomicZone of the United States is a zone contiguous tothe territorial sea, including zones contiguous to

the territorial sea of the U.S., the Commonwealthof Puerto Rico, the Commonwealth of the NorthernMariana Islands (to the extent consistent with theCovenant and the United States Trusteeship Agree-ment), and United States overseas territories andpossessions. The Exclusive Economic Zone extendsto a distance 200 nautical miles from the baselinefrom which the breadth of the territorial sea ismeasured.

Exercise area. An area shown on charts within whichnaval, military, or aerial exercises are carried out.Also called military practice area.

Extinguished. A lighted aid which has failed to showa light signal.

Extrusion (border break). The extension of chartdetail outside the neatline.

Fairway. That part of a river, harbor, etc., wherethe main navigable channel for vessels of larger sizelies. The usual course followed by vessels enteringor leaving harbor. Also called ship channel. The word�fairway� has been generally interpreted to includeany navigable water on which vessels of commercehabitually move, and, therefore, embraces the wa-ter inside channel buoys where light-draft vesselsfrequently navigate and not merely the ship chan-nel itself.

Fairway buoy. A buoy marking the fairway in achannel. They are painted in black-and-white or red-and-white vertical stripes. Also called mid-chan-nel buoy.

Fall (falls). A cascade, waterfall, or cataract; the flowor descent of one body of water into another. (Usu-ally plural.)

Fan. A gently sloping, cone-shaped accumulation ofmaterial normally located at the mouth of a can-yon.

Fast land. Land inshore of the inner edge of a marsh;usually at or above the plane of mean high water.

Fast shoreline. The term �fast shoreline� refers tothe line appearing on a shoreline map that sepa-rates water from fast, natural uplands. This lineshould not be confused with the approximate backlimits of marsh or marine vegetation which is nor-mally compiled shoreward from an apparent shore-line and in lieu of the fast shoreline.

Fathom. The common unit of depth in the ocean forcountries using the English system of units, equalto 6 feet (1.83 meters). It is also sometimes used inexpressing horizontal distances, in which case 120


fathoms make one cable or very nearly 1/10 nauti-cal mile.

Fault. In geology, a break or shear in the earth�s crustwith an observable displacement between the twosides of the break, and parallel to the plane of thebreak.

Federal project depth. The design dredging depthof a channel constructed by the U.S. Army Corps ofEngineers; the project depth may or may not be thegoal of maintenance dredging after completion ofthe channel. For this reason federal project depthmust not be confused with Controlling depth.

Ferryboat. A vessel in which passengers, vehicles,and goods are conveyed over narrow waters.

Fill material. The term �fill material� means anymaterial used for the primary purpose of replacingan aquatic area with dry land or of changing thebottom elevation of any waterbody. The term doesnot include any pollutant discharged into the waterprimarily to dispose of waste.

Filtering. This is the process of selecting specific datawithin a specific source document for chart appli-cation.

Finger piers. Small piers which extend from a largermain pier.

Fiord (or fjord). A long narrow arm of the sea, run-ning up between high banks or cliffs, as on the coastof Norway. Often has a relatively shallow sill acrossits entrance.

Fish aggregating devices (FADs). Clusters of sub-merged hollow spheres tethered to a 5-foot diam-eter spherical surface buoy and cabled to heavy con-crete blocks on the seafloor to hold them in suspen-sion. FADs are deployed in depths of 480 to 9,000feet and at distances from 2 to 15 miles off shore.They are primarily used in the waters off the Ha-waiian Islands and to attract fish for commercialand recreational fishermen.

Fish havens. Areas established by private interests,usually sport fishermen, to simulate natural reefsand wrecks that attract fish. The reefs are con-structed by dumping assorted junk in areas whichmay be of very small extent or may stretch a con-siderable distance along a depth contour. Fish ha-vens are outlined and labeled on charts. Also calledfishery reefs.

Fishing ground. A water area in which fishing isfrequently carried on. Also called fishing area orFishing zone.

Fishing zone. The offshore zone in which exclusivefishing rights and management are held by thecoastal nation. The United States fishing zone,known as the Fishery Conservation Zone, is de-fined under P.L. 94-265. The law states, �The in-ner boundary of the Fishery Conservation Zone is aline conterminous with the seaward boundary ofeach of the coastal states, and the outer boundaryof such zone is a line drawn in such manner thateach point on it is 200-nautical miles from thebaseline from which the territorial sea is measured.�

Fish pound. A fixed fish trap of the barrier type. Alsocalled weir. It generally consists of a stone wall builtacross the mouth of a creek and of such height thatit can be covered only at high spring tide. At onepoint there is an opening which can be closed, thusretaining any fish that made their way into the creekon flood tide. When the opening is closed, the watercan pass through a grating in the door and whenthe creek is dry the fish are collected.

Fish (or fishing) stakes. Poles or stakes placed inshallow water to outline fishing grounds or to catchfish.

Fishtrap areas. Areas established by the U.S. ArmyCorps of Engineers in which traps may be built andmaintained according to established regulations. Thefish stakes which may exist in these areas are ob-structions to navigation and may be dangerous. Thelimits of fishtrap areas and a cautionary note areusually charted.

Fix. A position determined without reference to anyformer position. In concept, a fix is the commonintersection of two or more lines of position obtainedfrom simultaneous observations not dependent uponany former position. In normal practice, a fix is themost probable position derived from two or moreintersecting lines of position obtained from obser-vations made at nearly the same time and advancedor retired to a common time, the lines when num-bering three or more not intersecting at a commonpoint because of the errors associated with each line.

Fixed bridge. A single- or multiple-span bridge with-out a movable span. It has fixed vertical and hori-zontal clearance.

Flagpole. A label on a nautical chart which indicatesa single staff from which flags are displayed. Theterm is used when the pole is not attached to a build-ing. The label flagstaff is used for a flagpole risingfrom a building.

Flag tower. A label on a nautical chart which indi-cates a scaffoldlike tower from which flags are dis-


played.

Flashing light. A light in which the total duration oflight in a period is shorter than the total durationof darkness, and appearances of light (flashes) areusually of equal duration. The term is commonlyused for a single-flashing light, a flashing light inwhich a flash is regularly repeated (at a rate of lessthan 50 flashes per minute).

Flash tube. A discharge lamp, operated with elec-tronic equipment, giving a high light output for avery brief period, capable of repetition.

Flat. A level tract lying at a small depth below thesurface of water, or alternately covered and left bareby the tide (�tidal flat,� �mud flat�).

Float. A float is a floating structure, usually rectan-gular in shape, which generally serves as a landingor pierhead.

Floating aid. A buoy, secured in its assigned posi-tion by a mooring.

Floating breakwater. A breakwater consisting of aseries of logs or timbers chained or lashed togetherand secured by chains or cables attached to anchorsor large blocks of stone, so as to form a protectedbasin for the mooring or anchoring of vessels.

Floating dock. A form of dry dock consisting of afloating structure of one or more sections, whichcan be partly submerged by controlled flooding toreceive a vessel, then raised by pumping out thewater so that the vessel�s bottom can be exposed.See also: Graving dock.

Flood. Tidal current moving toward land or up a tidalstream. The opposite is Ebb.

Flood current. The movement of a tidal current to-ward the shore or up a tidal river or estuary.

Floodgate. A gate for shutting out, admitting, or re-leasing a body of water; a sluice.

Flood plain. Belt of low flat ground bordering astream channel that is flooded when runoff exceedsthe capacity of the stream channel.

Floor. The bed or bottom of the ocean. A compara-tively level valley bottom; any low-lying groundsurface.

Fog detector. A device used to automatically deter-mine conditions of visibility which warrant the turn-ing on or off of a sound signal or additional lightsignals.

Fog signal. Generic term for sound and wireless sig-nals employed aboard ship and on shore stations infog, mist, falling snow, or heavy rainstorms.

Folio charts. These NOAA charts consist of two tofour sheets, are printed front and back, folded, andare bound in a protective cardboard jacket.

Foot. (1) The bottom of a slope, grade, or declivity. Aterm for the lower part of any elevated land form.(2) A unit of length defined to be 1/3 of a yard andequal in the United States, since 1866, to exactly1200/3937 of a meter.

Foothill. One of the lower subsidiary hills at the footof a mountain, or of higher hills. (Commonly usedin the plural.)

Fore and aft bridge. A series of connecting gang-ways between the forward and after bridges or be-tween a bridge house and forecastle deck or poopdeck. It is commonly found on tankers, where suchan installation is desirable due to the slippery con-dition of the upper deck. Sometimes called monkeybridge. Also called connecting bridge, flying bridge,catwalk.

Foreland. A cape or promontory.

Foreshore. In legal terminology, the strip of landbetween the high- and low-water marks that is al-ternately covered and uncovered by the flow of thetide. In coastal engineering work, it is defined asthe part of the shore that lies between the crest ofthe berm and the ordinary low-water mark, whichis ordinarily traversed by the uprush and backrushof the waves as the tide rises and falls; the fore-shore would thus extend farther inshore than theshore. See also: Shore.

Foreshore (according to Coastal Engineering.)That part of the shore lying between the crest ofthe seaward berm (or the upper limit of wave washat high tide) and the ordinary low-water mark. Seealso: Foreshore (according to Riparian Law).

Foreshore (according to Riparian Law). The stripof land between the high- and low-water marks thatis alternately covered and uncovered by the flow ofthe tide. See also: Foreshore (according toCoastal Engineering).

Fork. One of the major bifurcations of a stream; abranch.

Form line. Broken lines resembling contour lines butrepresenting no actual elevations, which have beensketched from visual observation or from inadequateor unreliable map sources, to show collectively the


shape of the terrain rather than the elevation.

Foul area. An area of numerous uncharted dangersto navigation. The area charted serves as a warn-ing to the mariner that all dangers are not chartedindividually and that navigation through the areamay be hazardous. The term �foul� is not applied toa soft continuum with indefinite boundaries, suchas mud or sand; to areas congested with marinevegetation, such as kelp or grass in water; or tomaterials not likely to cause damage to a vessel.

Foul bottom. A hard, uneven, rocky, or obstructedbottom having poor holding qualities for anchors,or one having rocks or wreckage that would endan-ger an anchored vessel.

Foul ground. An area unsuitable for anchoring, tak-ing the ground, or ground fishing due to being strewnwith rocks, boulders, coral, or obstructions.

Fractional scale. The scale expressed as a fraction(termed the �representative fraction� or �R.F.� ofthe chart or map) in which the numerator is unityand the denominator is the number that the unitdistance must be multiplied by in order to obtainits distance on the ground in the same units, thus1/12,000. Also used in the form 1:12,000 and 1-12,000. Sometimes referred to as natural scale. Seealso: Scale.

Fracture zone. A zone of unusually irregular topog-raphy of the seafloor averaging 60-nautical milesin width and normally greater than 1,000-nauticalmiles in length. This zone is characterized by largeseamounts, steep-sided, or nonsymmetrical ridges,troughs, or escarpments.

Fringing reef. A reef closely attached to a shore, ascontrasted with a barrier reef, which is separatedfrom the shore by a lagoon.

Gap. A deep notch, ravine, or opening between hillsor in a ridge or mountain chain; a steep-sided de-pression cutting transversely across a ridge or rise.

General charts. These NOAA charts of the coast arepublished at scales from 1:150,000 to 1:600,000, andare intended for coastal navigation when a courseis well offshore but can be fixed by landmarks,lights, buoys, and characteristic soundings.

Generalization. Selection and simplified represen-tation of detail appropriate to the scale and/or thepurpose of a map.

Generalization of detail. A term used to indicatethat the least essential information is not shown ona chart. The purpose of generalization is primarily

to avoid over crowding charts where space is verylimited. It also serves to reduce the correctionalmaintenance needed and to induce navigators, atleast of deeper draft vessels, to use charts of largerscales.

Geodesy. (1) The science concerned with determin-ing the size and shape of the earth. (2) The sciencethat locates positions on the earth and determinesthe earth�s gravity field. The definition can be ex-tended to other planetary bodies. (3) The branch ofsurveys in which the curvature of the earth mustbe taken into account when determining directionsand distances.

Geodetic coordinates. The quantities of latitude,longitude, and height (ellipsoid), which define theposition of a point on the surface of the earth withrespect to the reference spheroid. Also impreciselycalled geographic coordinates.

Geodetic datum. (Also called horizontal or geodeticdatum.) The adopted position in latitude and longi-tude of a single point to which the charted featuresof a vast region are referred.

Geodetic latitude. The angle which the normal at apoint on the reference spheroid makes with theplane of the geodetic equator.

Geodetic longitude. The angle between the plane ofthe geodetic meridian and the plane of an initialmeridian, arbitrarily chosen.

Geodetic position. A position of a point on the sur-face of the earth expressed in terms of geodetic lati-tude and geodetic longitude. A geodetic positionimplies an adopted geodetic datum.

Geographic. Signifying basic relationship to the earthconsidered as a globe-shaped body. The term geo-graphic is applied alike to data based on the geoidand on a spheroid. In geodetic surveys in this coun-try, coordinated data consisting of latitudes, longi-tudes, azimuths, and lengths of lines, are recordedand published under the general title of geographicpositions.

Geographic and other names. The term �geo-graphic names� refers to localities, natural features,and artificial waterways. The names do not applyto other artificial objects or features such as roads,bridges, parks, buildings, and stadiums.

Geographical coordinates. Spherical coordinatesdefining a point on the surface of the earth, usuallylatitude and longitude. Also called terrestrial coor-dinates.


Geographic latitude. A general term applying aliketo astronomic and geodetic latitudes.

Geographic longitude. A general term applyingalike to astronomic and geodetic longitudes.

Geographic meridian. A general term applying aliketo astronomic and geodetic meridians.

Geographic position. The position of a point on thesurface of the earth expressed in terms of latitudeand longitude, either geodetic or astronomic.

Geographic range. The greatest distance the curva-ture of the earth permits an object of a given heightto be seen from a particular height of eye withoutregard to luminous intensity or visibility conditions.

Geyser. A spring which throws forth intermittent jetsof heated water or steam.

Glacial drift. Sand, clay, or boulders transported byglaciers to their present locations.

Glacial gorge. A deeply cut valley in U-shaped cross-section, resulting from glacial erosion.

Glacial lake. A lake, the basin of which has beencarved by glacial action; also a body of water heldin place by the damming action of a glacier.

Glacier. A mass of snow and ice continuously mov-ing from higher to lower ground or, if afloat, con-tinuously spreading. The principal forms of glaciersare ice sheets, ice shelves, ice caps, ice piedmonts,and various types of mountain glaciers.

Glen. A secluded and small narrow valley; a dell, dale,or vale.

Gnomonic chart. A chart constructed on the gno-monic projection and often used as an adjunct fortransferring a great circle to a Mercator chart. Com-monly called Great-Circle Chart.

Gorge. A canyon, a rugged and deep ravine or gulch.

Grade. A slope of uniform inclination.

Gradient. Any departure from the horizontal; a grade;a slope; a part of a road or railroad which slopesupward or downward; frequently used in connec-tion with the slope of streams.

Gradient tints. Tinted areas on a map or chart, nor-mally in the form of bands following the contourpattern, used to indicate ranges of altitude.

Graphic scale (also called linear scale). A lineor bar on a map or chart subdivided to representdistances on the earth in various units, e.g., nauti-

cal miles, statute miles, yards, feet, kilometers, etc.

Grass in water. For mapping purposes, is anonwoody stemmed vascular plant (which may ormay not be a true grass), that is attached to thebottom below the sounding datum. Grass in wateris normally mapped only when the vegetation growsto the water surface.

Gravel. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. See under: Stones.

Graving dock. A form of dry dock consisting of anartificial basin fitted with a gate or caisson, intowhich vessels can be floated and the water pumpedout to expose the vessels� bottoms. The term is de-rived from the term used to describe the process ofburning barnacles and other accretions from a ship�sbottom. See also: Floating dock.

Great circle. The line of intersection of the surface ofa sphere and any plane which passes through thecenter of the sphere.

Great circle course. The direction of the great circlethrough the point of departure and the destination,expressed as the angular distance from a referencedirection, usually north, to the direction of the greatcircle. The angle varies from point to point alongthe great circle.

Greenwich Meridian. The meridian of the RoyalObservatory, Greenwich, England. Adopted in 1884by a conference of nations as the initial, or zero, oflongitudes for all nations.

Gridiron. A gridiron or careening grid is a flat frame,usually of parallel timber baulks, erected on theforeshore so that a vessel may dry out on it for paint-ing or repair at low water.

Groin. A structure projecting from shore and designedto break the current and reduce erosion and fill outthe shore by a deposition of new materials. Groinsmay be classified as permeable or impermeable:impermeable groins have solid or nearly solid struc-ture, permeable groins have openings through themof sufficient size to permit passage of appreciablequantities of littoral drift.

Grotto. A small, picturesque cave, vault, or cavern.

Ground. To touch bottom or run aground. In a seri-ous grounding the vessel is said to strand.

Group repetit ion interval . Of a part icularLORAN-C chain, the specified time interval for allstations of the chain to transmit their pulse groups.For each chain a minimum group repetition inter-val (GRI) is selected of sufficient duration to pro-


vide time for each station to transmit its pulse groupand additional time between each pulse group sothat signals from two or more stations cannot over-lap in time anywhere within the coverage area.

Group repetition interval code. The group repeti-tion interval in microseconds divided by ten.

Gulch. A small ravine; a small, shallow canyon withsmoothly inclined slopes and steep sides.

Gulf. A tract of water within an indentation or curveof the coastline, in size between a bay and a sea�the Gulf of California, for example.

Gully. Small valley cut into soft sediments on thecontinental shelf or continental slope. A small chan-nel recently cut by running water; smaller than agulch or ravine.

Gut. A narrow passage or contracted strait connect-ing two bodies of water.

Hachures. (1) Short lines on topographic maps or nau-tical charts to indicate the slope of the ground orthe submarine bottom. They usually follow the direc-tion of the slope. (2) Inward-pointing short lines or�ticks� around the circumference of a closed con-tour indicating a depression or a minimum.

Half-tide level. The level midway between mean highwater and mean low water. It may differ slightlyfrom mean sea level. Also called mean tide level.

Hammock. Variation of hummock, but usually char-acterized more by soil type and vegetation than byelevation. (Southern U.S., especially Florida andgulf coast.)

Harbor. A water area nearly surrounded by land orartificial dikes forming a safe anchorage for ships.

Harbor charts. NOAA charts published at scales of1:50,000 and larger, and intended for navigating inharbors and smaller waterways and for anchorage.

Harbor line. The line beyond which wharves andother structures cannot be extended.

Harbormaster. A local official who has charge ofmooring and berthing of vessels, collecting harborfees, and other duties.

Harbor of refuge. A harbor provided as a temporaryrefuge on a stormy coast for the convenience of pass-ing ships. Also called port of refuge. It may or maynot be part of a shipping port.

Harbor reach. The reach of a winding river or estu-ary which leads directly to the harbor.

Hatching. The drawing or engraving of fine, parallel

or crossed lines to show shading.

Head. A precipitous cape, or promontory. See also:Headland.

Heading. The horizontal direction in which a shipactually points or heads at any instant, expressedin angular units from a reference direction, usu-ally from 000° at the reference direction clockwisethrough 360°.

Headland. In common usage, a land mass having aconsiderable elevation. In the context of the law ofthe sea, elevation is not an important attribute anda headland may be the apex of a salient of the coast,the point of maximum extension of a portion of theland into the water, or a point on the shore at whichthere is an appreciable change in direction of thegeneral trend of the coast.

Heath. A tract of wasteland; peat bog, usually cov-ered by a low shrubby growth, but may have scat-tered small open water holes. (Local in easternMaine.)

Height. The vertical distance of an object, point, orlevel above the ground or other established refer-ence plane.

Height of tide. The vertical distance from the chartdatum to the level of the water at any time.

Highland(s). High or elevated land; a lofty headlandor cliff. The mountainous or elevated part of anycountry, occasionally also in the names of geograph-ical districts.

Hill. A natural elevation of the earth�s surface, smallerthan a mountain. See also: Knoll.

Hillock. A small hill.

Holding ground. An expression usually used with amodifying adjective to indicate the quality of theholding power of the material constituting the bot-tom of an anchorage, e.g., of good (or poor) holdingground.

Hole. A small bay, as Woods Hole, Massachusetts.(Local in New England.)

Hollow. A small ravine; a low tract of land encom-passed by hills or mountains.

Hook. Something resembling a hook in shape, par-ticularly: (a) a spit or narrow cape of sand or gravel,which turns landward at the outer end; or (b) asharp bend or curve, as in the stream.

Hulk. The hull or portion of the hull of a derelict ves-sel, usually without superstructure or other appur-


tenance. A major portion of the hulk is usually vis-ible at some stage of tide.

Hummock. A rounded elevation of ground, of limitedsize, rising out of a level surface (often swamp), fre-quently densely wooded.

Hydrographer. One who studies and practices thescience of hydrography.

Hydrographic survey. A survey made in relation toany considerable body of water, such as a bay, har-bor, lake, or river for the purposes of determinationof channel depths for navigation, location of rocks,sand bars, lights, and buoys; and in the case of riv-ers, made for flood control, power development, navi-gation, water supply, and water storage.

Hydrography. (1) The science which deals with themeasurements and description of the physical fea-tures of the oceans, seas, lakes, rivers, and theiradjoining coastal areas, with particular referenceto their use for navigational purposes. (2) That partof topography pertaining to water and drainage fea-tures.

Hyperbolic line of position. A line of position inthe shape of a hyperbola, determined by measuringthe difference in distance to two fixed points, e.g.,LORAN-C lines of position.

IALA Maritime Buoyage System. As designed bythe International Association of Lighthouse Authori-ties, a new uniform system of maritime buoyage,which is expected to be implemented by most mari-time nations. However, within the single systemare two international buoyage regions, designatedas region A and region B, where lateral marks dif-fer only in the colors of port and starboard handmarks. In region A, red is to port on entering; inregion B, red is to starboard on entering. The sys-tem may be briefly described as a combined cardi-nal and lateral system. The system applies to allfixed and floating marks, other than lighthouses,sector lights, leading lights and marks, lightshipsand large navigational buoys. The system providesfive types of marks which may be used in combina-tion: lateral marks, used in conjunction with a con-ventional direction of buoyage, are generally usedfor well-defined channels. Where a channel divides,a modified lateral mark may be used to indicate thepreferred route. Lateral marks may differ betweenbuoyage regions A and B. Cardinal marks used inconjunction with the mariner�s compass, indicatewhere the mariner may find navigable water. Iso-lated danger marks indicate isolated dangers of lim-ited size that have navigable water all around them.

Safe water marks to indicate that there is navi-gable water around their position, e.g., mid-chan-nel marks. Special marks, not primarily intendedto assist navigation, indicate an area or feature re-ferred to in nautical documents.

Ice buoy. A lighted or unlighted buoy of sturdy con-struction that replaces a buoy more easily damagedduring the winter ice season.

Improved channels. Dredged channels under thejurisdiction of the U.S. Army Corps of Engineers,and maintained to provide an assigned controllingdepth. Symbolized on the nautical charts by black,dashed lines to represent the side limits, with thecontrolling depth and date of ascertainment giventogether with a tabulation for more detailed infor-mation.

Index contour line. A contour line accentuated by aheavier line weight to distinguish it from interme-diate contours. Index contours are usually shownas every fifth contour with their assigned values, tofacilitate reading elevations.

Inland rules of the road. Rules to be followed by allvessels while navigating upon certain inland wa-ters of the United States.

Inland sea. A body of water nearly or completely sur-rounded by land, especially if very large or com-posed of salt water. If completely surrounded byland, it is usually called a lake. This should not beconfused with closed sea, that part of the ocean en-closed by headlands, within narrow straits, etc., orwithin the territorial jurisdiction of a country.

Inlet. A narrow waterway or a gap in the land, whichconnects a small body of water with a larger body;a small narrow bay or creek. A narrow body of wa-ter extending into the land from a larger body ofwater. A long, narrow inlet with gradually decreas-ing depth inward is called a ria. Also called arm,tongue.

Inner harbor. The part of a harbor more remote fromthe sea, as contrasted with the outer harbor. Theseexpressions are usually used only in a harbor thatis clearly divided into two parts, as by a narrowpassageway or artificial structures. The inner har-bor generally has additional protection and is oftenthe principal berthing area.

Inoperative. Sound signal or radionavigation aid outof service due to a malfunction.

Inset. In cartography (1) a small area outside theneatlines of map or chart included within the


neatlines or borders to avoid publishing a separategraphic of the small area alone; (2) a representa-tion of a small area on a larger scale (e.g., town-plan inset), or of a large area at a smaller scale(e.g., orientation inset); (3) any information, notnormally appearing within the geographic limits ofa map, which has been enclosed by border lines andincluded within the map neatlines. Insets are al-ways placed in areas where important features willnot be covered.

Inshore. The zone of variable width between theshoreface and the seaward limit of the breaker zone.

Intermediate contour line. A contour line drawnbetween index contours. Depending on the contourinterval, there are three or four intermediate con-tours between the index contours.

Intermittent stream. A stream or portion of astream that flows only in direct response to precipi-tation. It receives little or no water from springsand no long-continued supply from melting snow orother sources. It is dry for a large part of the year,ordinarily more than 3 months.

International Great Lakes Datum (IGLD) (1955).Mean water level at Pointe-au-Père, Quebec,Canada, on the Gulf of St. Lawrence, over the pe-riod 1941 through 1956, from which dynamic el-evations throughout the Great Lakes region aremeasured. The term is often used to mean the en-tire system of dynamic elevations rather than justthe reference water level.

International Hydrographic Bureau (IHB). Anorganization founded in 1921 for the purpose of es-tablishing a close and permanent association amonghydrographic offices of its states members. TheBureau�s main object is to encourage coordinationof hydrographic work with a view to rendering navi-gation easier and safer throughout the world. Aconvention agreed by member states became effec-tive in 1970 making the IHB the executive organ ofthe International Hydrographic Organization(IHO).

International Hydrographic Organization(IHO). Organized in 1970 by ratification of the Con-vention on the International Hydrographic Organi-zation, IHO legally assumed the international in-tergovernmental responsibilities formerly held bythe International Hydrographic Bureau (IHB),which now serves as the administrative or head-quarters facility for IHO. IBH was founded in 1921.

International Maritime Organization (IMO).(Formerly the Inter-governmental Maritime Con-

sultative Organization (IMCO).) Established in1959 (as the UN-sponsored international agency forthe promotion of maritime safety and marine pollu-tion prevention), IMO is mainly concerned withmaritime safety and coordinates work relating toatomic propulsion, aviation, health, labor, meteo-rology, oceanography, and telecommunications.

International rules. The rules of the road estab-lished by agreement between maritime nations,governing the navigation of the high seas.

International rules of the road. The rules of navi-gation that are applicable to the water areas sea-ward of the lines established by the U.S. CoastGuard.

Interrupted quick-flashing light. A quick light inwhich the sequence of flashes is interrupted by regu-larly repeated eclipses of constant and long dura-tion.

Intracoastal waterway. An inside protected routeextending through New Jersey; from Norfolk, VA,to Key West, FL; across Florida, from St. LucieInlet to Fort Myers, Charlotte Harbor, Tampa Bay,and Tarpon Springs; and from Carabelle, FL, toBrownsville, TX.

Island. A land area (smaller than a continent) ex-tending above and completely surrounded by waterat mean high water; an area of dry land entirelysurrounded by water or a swamp; an area of swampentirely surrounded by open water.

Island shelf. A zone adjacent to an island and ex-tending from the low-water line to a depth at whichthere is a marked increase of slope to greater depth.

Island slope. A declivity from the outer edge of anisland shelf into greater depths.

Islet. A small island.

Isogonic. A line connecting points of equal magneticvariation. Also called isogonic line, isogonal.

Isogonic chart. A chart showing magnetic variationwith isogonic lines and the annual rate of changein variation with isoporic lines.

Isoporic line. A line connecting points of equal an-nual rate of change of any magnetic element. Alsocalled isopor.

Isthmus. A narrow strip of land connecting two largerbodies of land.

Jetty. A structure built out into the water to restrainor direct currents, usually to protect a river mouthor harbor entrance from silting. On open seacoasts,


a structure extending into a body of water, and de-signed to prevent shoaling of a channel by littoralmaterials, and to direct and confine the stream ortidal flow. Jetties are built at the mouth of a riveror tidal inlet to help deepen and stabilize a channel.

Junction. (1) A place of joining of two channels, asthat of tributary with a main river. (2) In levelling,the place where two or more lines of levels are con-nected together. (3) In hydrographic survey, thejoining of two adjacent survey sheets.

Junction buoy. A buoy which, when viewed from avessel approaching from the open sea or in the samedirection as the main stream of flood current, or inthe direction established by appropriate authority,indicates the place at which two channels meet. Seealso: Bifurcation buoy.

Kelp. One of an order of unusually large, blade-shaped, or vinelike brown algae. Kelp is so fre-quently associated with rocky bottoms, and there-fore possible dangers to navigation, that it shouldnot be confused with, or compiled as, other marinevegetation. Kelp of one species or another is widelyfound in the cold oceans of the world.

Key. A low island or reef; a cay.

Kill. A channel, creek, or stream, as the kills betweenStaten Island, NY, and Bergen Neck, NJ.

Knob. A rounded hill or mountain, especially an iso-lated one.

Knoll. A small round hill; a mound; a seamount ris-ing less than 500 fathoms from the seafloor andhaving a pointed or rounded top.

Knot. A unit of speed defined as 1 international nau-tical mile per hour.

Lagoon. (1) A shallow sound, pond, or lake generallyseparated from the open sea. (2) A body of waterenclosed by the reefs and islands of an atoll.

Lake. (1) A standing body of open water that occurs ina natural depression fed by one or more streamsfrom which a stream may flow, that occurs due tothe widening or natural blockage or cutoff of a riveror stream, or that occurs in an isolated natural de-pression that is not a part of a surface river orstream. (2) A standing body of open water createdby artificially blocking or restricting the flow of ariver, stream, or tidal area. (3) Any standing bodyof inland water, generally of considerable size. Thereare exceptions such as the lakes in Louisiana, whichare open to or connect with the Gulf of Mexico. Oc-casionally a lake is called a sea, especially if verylarge and composed of salt water.

Landfall. The first sighting of land when approachedfrom seaward. By extension, the term is sometimesused to refer to the first contact with land by othermeans, e.g., by radar.

Landing. A place where boats receive or dischargepassengers, freight, etc. See also: Wharf.

Landmark. In marine terminology, a landmark isan object or feature of known position that is con-spicuous to the mariner and so located that it canbe used for navigation. A landmark should bereadily identifiable by the mariner and locatedwhere it will be visible through a useful range oftravel. An object that is conspicuous at one point,but quickly becomes lost in background clutter orhidden from view by obstructions as the marinerprogresses is of limited value.

Landslide. Earth and rock which becomes loosenedfrom a hillside by moisture or snow, and slides orfalls down the slope.

Lane. An established route as an air lane or shippinglane. In an electronic radiolocation lattice, the zonebetween two lines on which measured values, ex-pressed in terms of the system�s electronic unit(wavelength or microsecond), are whole numbersand are one unit apart.

Large navigational buoy (LNB or LANBY). (1) Alarge buoy designed to take the place of a lightshipwhere construction of an offshore light station isnot feasible. These 40-foot diameter buoys may showsecondary lights from heights of about 36 feet abovethe water. In addition to the light, these buoys maymount a radiobeacon and provide sound signals. Astation buoy may be moored nearby. Called light-house buoy in British terminology. (2) A 40-footdiameter, automated discus-shaped buoy used toreplace light vessels.

Lateral system. (1) A system of aids to navigation inwhich buoys, daybeacons, and minor lights are as-signed colors and shapes in accordance with theirrespective location in relation to safe water. (2) Asystem of aids to navigation in which the shape,color, and number distinction are assigned in ac-cordance with their location in respect to navigablewaters. When used to mark a channel, they areassigned colors to indicate the side they mark andnumbers to indicate their sequence along the chan-nel. The lateral system is used in the United StatesIn the cardinal system, the aids are assigned shape,color, and number distinction in accordance withlocation relative to the nearest obstruction.

Latitude. Angular distance from a primary great


circle or plane. Terrestrial latitude is angular dis-tance from the equator, measured northward orsouthward through 90° and labeled �N� or �S� toindicate the distance between the plumb line andthe plane of the celestial equator. Geodetic or topo-graphical latitude at a station is angular distancebetween the plane of the geodetic equator and a nor-mal to the ellipsoid. Geocentric latitude is the angleat the center of the reference ellipsoid between thecelestial equator and a radius vector to a point onthe ellipsoid. Geodetic and sometimes astronomi-cal latitude are also called geographic latitude.Geodetic latitude is used for charts.

Latitude scale. The subdivided east and west bor-ders of a Mercator chart into degrees and minutes;a variant of the graphic scale, since a minute oflatitude is very nearly equal to a nautical mile.

Lava. The fluid or semifluid matter flowing from avolcano. The substance that results from the cool-ing of the molten rock. Part of the ocean bed iscomposed of lava.

Lead. The weight attached to a line. A sounding leadis used for determining depth of water. A handlead is a light sounding (7 lbs to 14 lbs), usuallyhaving a line of not more than 25 fathoms. A deep-sea lead is a heavy sounding lead (about 30 lbs to100 lbs), usually having a line 100 fathoms or morein length. A light deep-sea lead (30 lbs to 50 lbs),used for sounding depths of 20 to 60 fathoms is calleda coasting lead. A type of sounding lead used with-out removal from the water between soundings iscalled a fish lead. A drift lead is one placed on thebottom to indicate movement of a vessel. To heavethe lead is to take a sounding with a lead.

Leadline. A line, graduated with attached marks andfastened to a sounding lead, used for determiningthe depth of water when making soundings by hand.The leadline is usually used in depths of less than25 fathoms. Also called sounding line.

Leading light. A light so located that vessels maysteer directly for it until close aboard, when a newcourse is taken.

Ledge. (1) A rocky formation connected with and fring-ing the shore and generally uncovered at the sound-ing datum. (2) A rocky formation continuous withand fringing the shore. The area that uncovers isusually represented on charts by symbols.

Left bank. That bank of a stream or river on the leftof an observer facing in the direction of flow, or down-stream. See also: Right bank.

Leg. (1) Each straight section of a traverse. (2) Onepart of a craft�s track consisting of a single courseline.

Legend. (1) A description, explanation, table of sym-bols, and other information printed on a map orchart to provide a better understanding and inter-pretation of it. The title of a map or chart formerlywas considered part of the legend, but this usage isobsolete. (2) An artificial bank confining a streamchannel or limiting adjacent areas subject to flood-ing. (3) On the seafloor, an embankment borderinga canyon, valley, or sea channel.

Levee. (1) An artificial bank confining a stream chan-nel or limiting adjacent areas subject to flooding.(2) On the seafloor, an embankment bordering acanyon, valley, or seachannel.

Light. The signal emitted by a lighted aid to naviga-tion; a piece of illuminating apparatus; a lightedaid to navigation on a fixed structure.

Lighthouse. A building on some conspicuous point ofthe coast, a pier or jetty, an island or rock, fromwhich a light is exhibited at night as an aid to navi-gation. All maritime nations have government de-partments responsible for the establishment andmaintenance of lighthouses.

Light List. (1) A publication giving detailed informa-tion regarding lighted navigational aids and fog sig-nals. The name and location of the lighted aids,their characteristics, heights, range, structure de-scription, and other pertinent remarks are given.(2) Light List, published by the U.S. Coast Guardin five volumes, covers the waters of the UnitedStates and its possessions including the IntracoastalWaterway, the Great Lakes (both U.S. and certainaids on the Canadian shores), and the MississippiRiver and its navigable tributaries. In addition tothe information on lighted aids, the Light List givesinformation on unlighted buoys, radiobeacons, ra-dio direction finder calibration stations, daybeacons,RACONs, etc. (3) List of Lights, published by theNIMA in seven volumes, covers waters other thanthe United States and its possessions. In additionto the information on lighted aids, the List of Listsprovides information on storm signals, signal sta-tions, radio direction finder stations, radiobeacons,etc.

Light List Number (LLNR). The number used toidentify a navigational light in the Light List. Thisnumber should not be confused with �InternationalNumber,� which is an identifying number assignedby the International Hydrographic Organization.The international number is in italic type and is


located under the Light List number in the LightList. Sometimes called list of lights number.

Light sector. (1) As defined by bearings from sea-ward, the sector in which a navigational light isvisible or in which it has a distinctive color differ-ent from that of adjoining sectors, or in which it isobscured. (2) The arc over which a light is visibledescribed in degrees true as observed from a vesseltoward the light.

Lightship. A distinctively marked vessel providingaids to navigation services similar to a light sta-tion, i.e., a light of high intensity and reliability,sound signal, and radiobeacon, and moored at a sta-tion where erection of a fixed structure is not fea-sible. The chart symbol represents the approxi-mate location of the anchor. Also called light ves-sel. Lightships are no longer used in the UnitedStates.

Light station. A manned station providing a lightusually of high intensity and reliability. It mayalso provide sound signal and radiobeacon services.In many instances, sound signals, radiobeaconequipment, and operating personnel are housed inseparate buildings near the light structure.

Line feature. A cartographic feature with the geom-etry of a line, i.e., defined by a sequence of connectedpoints. Represented on a map by a line of certainwidth or type, e.g., dashed, dotted, double, a sequenceof symbols.

Line of soundings. A series of soundings obtainedby a vessel underway, usually at regular intervals.In piloting, this information may be used to deter-mine an estimated position, by recording the sound-ings at appropriate intervals (to the scale of thechart) along a line drawn on transparent paper orplastic, to represent the track, and then fitting theplot to the chart, by trial and error. A vessel ob-taining soundings along a course line, for use inmaking or improving a chart, is said to run a lineof soundings.

Littoral. Pertaining to the shore, especially of thesea; a coastal region. Used coextensively with �ri-parian.� See also: Riparian lands.

Littoral current. A current in the littoral zone suchas a longshore or rip current.

Littoral state. One that borders on the sea or GreatLakes. Corresponds to Riparian State, which bor-ders on a river. See also: Riparian lands.

Littoral zone. In coastal engineering, the area from

the shoreline to just beyond the breaker zone. Inbiological oceanography, it is that part of the benthicdivision extending from the high-water line out to adepth of about 200 meters. The littoral system isdivided into a eulittoral and sublittoral zone, sepa-rated at a depth of about 50 meters. Also, frequentlyused interchangeably with �intertidal zone.�

Local magnetic disturbance. An anomaly of themagnetic field of the earth, extending over a rela-tively small area, due to local magnetic influences.Also called: local attraction, magnetic anomaly.

Lock. A basin in a waterway with caissons or gates ateach end by means of which vessels are passed fromone water level to another without materially af-fecting the higher level. To lock a vessel means topass a vessel through a lock.

Local Notice to Mariners (LNM). (1) A written docu-ment providing information pertaining to the con-dition of aids of navigation and the waterwayswithin each U.S. Coast Guard District that is ofinterest to the mariner. (2) A notice issued by eachU.S. Coast Guard District to disseminate impor-tant information affecting navigational safety withinthe District. The Local Notice to Mariners reportschanges to and deficiencies in aids to navigationmaintained by and under the authority of the U.S.Coast Guard. Other information includes channeldepths, new charts, naval operations, regattas, etc.Since temporary information, known or expected tobe of short duration, is not included in the weeklyNotice to Mariners published by National Imageryand Mapping Agency, the appropriate Local Noticeto Mariners may be the only source of such infor-mation. Much of the information contained in theLocal Notice to Mariners is included in the weeklyNotice to Mariners. The Local Notice to Marinersis published as often as required; usually weekly.It may be obtained by making application to theappropriate U.S. Coast Guard District Commander.

Log booms. Heavy logs chained or lashed togetherand moored or anchored so as to enclose and con-tain rafted logs.

Longitude. Angular distance, along a primary greatcircle, from the adopted reference point; the anglebetween a reference plane through the polar axisand a second plane through that axis. Terrestriallongitude is the arc of a parallel, or the angle at thepole, between the prime meridian and the meridianof a point on the earth, measured eastward or west-ward from the Prime meridian through 180°, andlabeled �E� or �W� to indicate the direction of mea-surement. Astronomical longitude is the angle be-


tween the plane of the prime meridian and the planeof the celestial meridian at a station and the planeof the geodetic meridian at Greenwich. Geodeticand sometimes astronomical longitude are alsocalled geographic longitude. Geodetic longitude isused in charting.

Longshore bar. A bar running roughly parallel tothe shoreline.

Lookout station. A distinctive structure or place onshore from which personnel keep watch upon eventsat sea or along the coast.

Lookout tower. Any tower surmounted by a smallhouse in which a watch is habitually kept, as dis-tinguished from an observation tower in which nowatch is kept.

Loran. (1) The designation of a family of electronicnavigational systems by which hyperbolic lines ofposition are determined by measuring the differ-ences in the time of reception of synchronized pulsesignals from two fixed transmitters. The name�LORAN� is derived from the words Long RangeNavigation. (2) A long-range, low-frequency (90 to110 kHz) radionavigation system by which a hy-perbolic line of position of high accuracy is obtainedby measuring the difference in the times of arrivalof pulse signals radiated by a pair of synchronizedtransmitters (master station and secondary station),which are separated by several hundred miles.

Lower lowwater datum (LLWD). An approxima-tion of mean lower low water that has been adoptedas a standard reference for a limited area and isretained for an indefinite period regardless of thefact that it may differ slightly from a better deter-mination of mean lower low water from a subse-quent series of observations. Used primarily forriver and harbor engineering purposes. ColumbiaRiver lower low water datum is an example.

Lowland. Low and relatively level land at a lowerelevation than adjoining districts.

Low-water datum (LWD). The dynamic elevationfor each of the Great Lakes and Lake St. Clair andthe corresponding sloping surfaces of the St. Marys,St. Clair, Detroit, Niagara, and St. Lawrence Riv-ers to which are referred the depths shown on thenavigational charts and the authorized depths fornavigation improvement projects.

Low-water line. The line where the established low-water datum intersects the shore. The plane of ref-erence that constitutes the low-water datum differsin different regions.

Loxodrome. A curve, on the surface of a sphere, in-tersecting all great circles of the sphere at a con-stant oblique angle, theoretically never reaching thepole while closely approaching it.

Luminous range. The greatest distance a light canbe seen given its nominal range (luminous inten-sity) and the existing meteorological visibility.

Magnetic annual change. The amount of magneticsecular change undergone in 1 year. Also calledannual change, annual magnetic change, annualrate, annual rate of change.

Magnetic disturbance. An irregular, large-ampli-tude, rapid change of the earth�s magnetic field,which occurs at approximately the same time world-wide. A magnetic disturbance is usually associ-ated with the occurrence of solar flares or otherstrong solar activity. Also called a magnetic storm.Sometimes, the daily magnetic variation is called amagnetic disturbance.

Magnetic meridian. The line having the directionof the magnetic needle at a given place; a verticalplane fixed by the direction taken by a perfect com-pass needle.

Magnetic north. The direction indicated by the north-seeking pole of a freely suspended magnetic needle,influenced only by the earth�s magnetic field.

Magnetic variation. A regular or irregular change,with time, of magnetic declination, dip, or inten-sity. In nautical and aeronautical navigation, andsometimes in surveying, the term magnetic varia-tion is used for magnetic declination. The regularmagnetic variations are: secular, the change fromyear to year in the same direction (which usuallypersists for many decades); annual, the change overa period of 1 year; and diurnal, the change over aperiod of 1 day (24 hours). Irregular variations,when sudden, worldwide, and severe, are known asmagnetic storms.

Mainland. The principal portion of a large land area.The term is used loosely to contrast a principal landmass from outlying islands and sometimes penin-sulas.

Major aid to navigation. An aid of considerable in-tensity, reliability, and range exhibited from fixedstructures or marine sites. Major aids are classi-fied as primary or secondary and are usuallymanned or remotely monitored.

Major light. A light of high intensity and reliabilityexhibited from a fixed structure or on a marine site


(except range light). Major lights include primaryseacoast lights and secondary lights. See also:Minor light.

Mangrove. This type includes the mangroves andstands of tree like plants that are predominantlymangrove. These plants are perennials that fre-quently create an apparent shoreline. Much of thisvegetation grows in the vicinity of the high water-line with overhanging and tangled growth that ob-scures the shoreline from the mariner.

Manmade (artificial) shoreline. This is the line ofcontact between the surface of a body of water andartificial land or features provided the artificial wa-terline is continuous with the natural shoreline.This is intended to include as artificial shorelinethe water along breakwaters, bulkheads, fill areas,jetties, and other features built out from the land.

Map. A representation, usually on a plane surface, ofall or part of the surface of the earth, celestial sphere,or other area; showing relative size and position,according to a given projection, of the physical fea-tures represented and such other information asmay be applicable to the purpose intended. Such arepresentation intended primarily for navigationaluse is called a chart. A method of representing allor part of the surface of a sphere or spheroid, suchas the earth, upon a plane surface is called a mapprojection. A planimetric map indicates only thehorizontal positions of features; a topographic mapindicates both horizontal and vertical position. Atopographic map showing relief by means of con-tour lines drawn at regular height intervals is calleda contour map. A relief map emphasizes relativeelevations or relief; a three-dimensional relief mapis called a relief model. The pattern on the under-side of extensive cloud areas, created by the vary-ing amounts of light reflected from the earth�s sur-face, is called a sky map. A chart which shows thedistribution of meteorological conditions over an areaat a given moment may be called a weather map.

Map bathymetric. Map delineating the form of thebottom of a body of water, or a portion thereof, bythe use of depth contours (isobaths).

Map digitization. Conversion of map data fromgraphic to digital form.

Map editing. The process of checking a map or chart,in its various stages of preparation, to ensure accu-racy, completeness, correct preparation, and inter-pretation of sources used, and legible and precisereproduction.

Map, isogonic. A map showing lines of constant

magnetic inclination for a particular base data(shown on the map). Lines of equal annual changein declination are generally also shown. If the mapis designed for use in navigation, it is called an iso-gonic chart.

Map, planimetric. A map which shows only thehorizontal positions of the features represented.Unlike a topographic map, a planimetric map doesnot show relief in measurable form. Natural fea-tures usually shown include rivers, lakes, and seas;mountains, valleys, and plains; forests, prairies,marshes, and deserts. Cultural features shown in-clude cities, farms, transportation routes, and pub-lic utility facilities; and political and private bound-ary lines.

Map projection. An orderly system of lines on a planerepresenting a corresponding system of imaginarylines on an adopted terrestrial or celestial datumsurface. Also the mathematical concept of such asystem.

Map projection, Mercator. A conformal map pro-jection of the so-called cylindrical type. The equa-tor is represented by a straight line true to scale;the geographic meridians are represented by paral-lel straight lines perpendicular to the line repre-senting the equator; they are spaced according totheir distance apart at the equator. The geographicparallels are represented by a second system ofstraight lines perpendicular to the family of linesrepresenting the meridians, and therefore, parallelwith the equator. Conformality is achieved by math-ematical analysis, the spacing of the parallels be-ing increased with increasing distance from theequator to conform with the expanding scale alongthe parallels resulting from the meridians being rep-resented by parallel lines. The Mercator map pro-jection is considered one of the most valuable of allmap projections, its most useful feature being thata line of constant bearing (azimuth) on a sphere isrepresented on the projection by a straight line.

Map relief. A map whose surface is shaped to repre-sent topography in a region. The most commonkind is the plastic relief map. This is made by print-ing an ordinary topographic map on a plastic sheet,which is then placed on a plaster mold that hasbeen carved to represent the topography. Heat andpressure are applied to fix the plastic sheet perma-nently into the shape of the mold. Another kind,less common and more costly but showing moredetail in greater accuracy, is the solid relief-map,made by carving the topography, etc., in a suitablesubstance, such as plaster, and then painting or


drawing further detail on the model. Also called aterrain model or relief model.

Map scale, equivalent. An equivalent scale is therelationship which a small distance on the mapbears to the corresponding distance on the earth,expressed as an equivalence. Usually, but not nec-essarily, the equivalence is expressed in differentspecified units; for example, 1 inch (on the map)equals 1 mile (on the ground).

Map scale, fractional. A fractional scale is the ra-tio which any small distance on the map bears tothe corresponding distance on the earth. It may bewritten in the form of a fraction: 1/10,000; or as aproportion 1:10,000.

Map scale, graphic (or bar). A line on a map sub-divided and marked with the distance which eachof its parts represents on the earth.

Map, topographic. (1) A map showing the horizon-tal and vertical locations of natural and artificialfeatures. It is distinguished from a planimetric mapby the presence of quantitative symbols showingthe relief. A topographic map usually shows thesame features as a planimetric map, but uses num-bered contour lines or comparable symbols to indi-cate elevations of mountains, valleys, and plains;in the case of hydrographic charts, symbols andnumbers are used to show depths in bodies of wa-ter. (2) A map whose principal purpose is to portrayand identify the natural or artificial features of theearth�s surface as faithfully as possible within thelimitations imposed by scale.

Margin data. All explanatory information given inthe margin of a map or chart which clarifies, de-fines, illustrates, and/or supplements the graphicportion of the sheet. Also called border data, bor-der information, margin information.

Marginal sea. The water area bordering a nation overwhich has exclusive jurisdiction, except for the rightof innocent passage of foreign vessels. It is a cre-ation of international law, although no agreementhas thus far been reached by the international com-munity regarding its width. It extends seawardfrom the low-water mark along a straight coast andfrom the seaward limits of inland waters where thereare embayments. The United States has tradition-ally claimed 3 nautical miles as its width and hasnot recognized the claims of other countries to awider belt. Also called territorial sea, adjacent sea,marine belt, maritime belt, and 3-mile limit.

Marginal wharf. A wharf flush with the general

adjacent shoreline and normally of concrete or as-phalt decking atop open-pile supports. This is thepredominant type of modern general cargo wharf.

Marina. A harbor facility for small boats, yachts, etc.,where supplies, repairs, and various services areavailable.

Marine. An adjective meaning relating to navigationor shipping; relating to or connected with the sea;used, or adopted for use at sea. Sometimes calledmaritime, but maritime more frequently applies tothat which borders on the sea.

Marine railway. A marine railway is a track, cradle,and winding mechanism for hauling vessels out ofthe water so that the hull can be exposed as in adry dock. This is also called a patent slip in Britishterminology.

Marine vegetation. For NOAA charting purposes,marine vegetation refers to permanent orsemipermanent vegetation or areas of vegetationgrowing at or seaward from the shoreline and pre-senting some significance to the mariner.

Marker. (1) A small automatic radiobeacon with arange of 4 to 6 miles located on a buoy, pierhead, orpiling structure. It is not intended for long-rangeaccurate bearings but serves as a local mark indi-cating a channel entrance, turning point, pierhead,etc., in or near a harbor. The use of two or morebeacons provides a �fix.� (2) That which marks some-thing; a marker beacon. See also: Radiobeacon.(3) A term used to describe an aid intended as aguide for normal surface navigation. It is gener-ally used to refer to any private unlighted or lightedfixed aid to navigation not established or maintainedby the U.S. Coast Guard and not listed in the LightList, which is erected to make minor channels. Theterm may also refer to markers for other specificpurposes (e.g., measured mile markers or dredgingrange).

Marker buoy. A temporary buoy used in surveyingto make a location of particular interest, such as ashoal or reef. See also: Station buoy.

Marl. One of several descriptors of the �nature of theseabed� used in Chart No. 1. A crumbling, earthydeposit, particularly one of clay mixed with sand,lime, decomposed shells, etc. Sometimes a layer ofmarl becomes quite compact. Part of the ocean bedis composed of marl. Marl is generally not a suit-able holding material for anchors. Anchoring inmarl requires an anchor with a pointed bill to pen-etrate the bottom.


Marsh. (1) An area of wet, often spongy ground thatis subject to frequent flooding or tidal inundations,but not considered to be continually underwater. Itis characterized by the growth of nonwoodystemmed, vascular plants, such as the bulrushes,cordgrasses, reeds, and other wetland species, andby the lack of trees. Marsh often forms a transitionbetween the open water and the dry uplands and isfrequently associated with an apparent shoreline.(2) A tract of low, wet ground, usually miry andcovered with rank vegetation. It may, at times, besufficiently dry to permit tillage or haycutting, butrequires drainage to make it permanently arable.

Matching. The act by which detail or information onthe edge, or overlap area, of a map or chart is com-pared, adjusted, and corrected to agree with theexisting overlapping chart.

Mattress. A mass of interwoven brush, poles, etc.,used to protect a bank from erosion.

Mean higher high water (MHHW). A tidal da-tum. The average of the higher high water heightof each tidal day observed over the National TidalDatum Epoch. For stations with shorter series,simultaneous observational comparisons are madewith a control tide station in order to derive theequivalent datum of the National Tidal Datum Ep-och.

Mean high water (MHW). A tidal datum. The av-erage of all the high-water heights observed overthe National Tidal Datum Epoch. For stations withshorter series, simultaneous observational compari-sons are made with a control tide station in order toderive the equivalent datum of the National TidalDatum Epoch.

Mean high water line (MHWL). The line on a chartor map, which represents the intersection of theland with the water surface at the elevation of meanhigh water. See also: Shoreline.

Mean lower low water (MLLW). A tidal datum. Theaverage of the lower low-water height of each tidalday observed over the National Tidal Datum Ep-och. For stations with shorter series, simultaneousobservational comparisons are made with a controltide station in order to derive the equivalent datumof the National Tidal Datum Epoch.

Mean low water (MLW). A tidal datum. The aver-age of all the low-water heights observed over theNational Tidal Datum Epoch. For stations withshorter series, simultaneous observational compari-sons are made with a control tide station in order to

derive the equivalent datum of the National TidalDatum Epoch.

Mean low water line (MLWL). The line on a chartor map which represents the intersection of the landwith the water surface at the elevation of mean lowwater.

Mean range of tide. The difference in height betweenmean high water and mean low water.

Mean sea level (MSL). (1) A tidal datum. The arith-metic mean of hourly heights observed over theNational Tidal Datum Epoch. Shorter series arespecified in the name; e.g., monthly mean sea leveland yearly mean sea level. (2) The average heightof the surface of the sea for all stages of the tideover a 19-year period, usually determined fromhourly height readings. A determination of meansea level that has been adopted as a standard forheights is called a sea level datum.

Measured mile. A length of 1-nautical mile, the lim-its of which have been accurately measured andare indicated by ranges ashore. It is used by ves-sels to calibrate logs, engine revolution counters,etc., and to determine speed.

Mercator projection. A conformal map projectionupon a plane, in which the latitude and longitudelines are straight parallel lines intersecting eachother at right angles, and in which the meridiansof longitude are spaced equally throughout the map,based on their distance apart at the equator, andthe distances between parallels are derived by amathematical analysis, their spacing bearing anexact relationship to the spreading of the merid-ians along a corresponding parallel.

Meridian. A north-south reference line, particularlya great circle through the geographical poles of theearth. The term usually refers to the upper branch,the half, from pole to pole, which passes through agiven place; the other half being called the lowerbranch.

Meridians. Imaginary planes passing through thepoles and measure longitudes east or west of theprincipal meridian of Greenwich. See also: Longi-tude.

Mesa. A flat-topped, rocky hill with steep sides.(Southwestern United States.)

Meter. The base unit of length in the InternationalSystem of Units, equal to 39.37008 inches, approxi-mately.

Metonic cycle. A period of almost 19 years or 235


lunations. Devised by Meton, an Athenian astrono-mer who lived in the fifth century B.C., for the pur-pose of obtaining a period in which new and fullmoon would recur on the same day of the year.

Metric system. Decimal system of weights and mea-sures based on the meter as a unit length and thekilogram as a unit mass.

Microwave. A very short electromagnetic wave, usu-ally considered to be about 30 centimeters to 1 mil-limeter in length. While the limits are not clearlydefined, it is generally considered as the wavelengthof a radar operation.

Microwave tower. A tower which carries microwavebroadcasters and receivers used in the transmis-sion of communications signals.

Mid-channel buoy. See Fairway buoy.

Middle latitude. Half the arithmetical sum of thelatitudes of two places on the same side of the equa-tor.

Mile. (1) A unit of distance. The nautical mile, or seamile, is used primarily in navigation. Nearly allmaritime nations have adopted the InternationalNautical Mile of 1,852 meters proposed in 1929 bythe International Hydrographic Bureau. The U.S.Departments of Defense and Commerce adopted thisvalue on July 1, 1954. Using the yard-meter con-version factor effective July 1, 1959 (1 yard = 0.9144meter, exactly), the International Nautical Mile isequivalent to 6076.11549 feet, approximately. Thegeographical mile is the length of one minute of arcof the equator, considered to be 6,087.08 feet. Thestatute mile or land mile (5,280 feet in the UnitedStates) is commonly used for navigation on riversand lakes, notably in the Great Lakes of NorthAmerica. (2) A unit of distance, variously defined.See also: Mile, nautical; Mile, statute.

Mile, international nautical. The nautical miledefined as exactly 1,852 meters length. It was pro-posed in 1929 by the International HydrographicBureau because of the variety of nautical miles thenin use. It has since been adopted by most maritimenations, and, on July 1, 1954, by the U.S. Depart-ment of Commerce and the U.S. Department of De-fense.

Mile, nautical. The U.S. nautical mile is defined asequal to the length of 1/60 of a degree of a greatcircle on a sphere having an area equal to the areaof an ellipsoid representing the earth�s surface. Itsvalue, calculated for the Clarke spheroid of 1866, is

1,853.248 m (6,080.2 feet); (compare with the inter-national nautical mile of 1,852 m (6,076.1 feet)).The U.S. nautical mile is also called a sea mile, ageographical mile, and a geographic mile. It maybe taken as equal to the length of a minute of arcalong the equator or a minute of latitude anywhereon a map. The nautical mile is used principally forstating distances over water. It is the unit of lengthused for defining the knot, a unit of speed definedas 1-nautical mile per hour.

Mile, statute. A unit of length defined to be exactly5,280 feet. It is used principally in stating distanceson land.

Minor aid to navigation. An unmanned,unmonitored light on a fixed structure showingusually low to moderate intensity; generally fittedwith light characteristics and dayboards in accor-dance with its lateral significance in the waterway.

Minor light. An automatic unmanned light on a fixedstructure usually showing low to moderate inten-sity. Minor lights are established in harbors, alongchannels, along rivers, and in isolated locations. Seealso: Major light.

Moat. An annual depression that may not be continu-ous, located at the base of a seamount or an island.

Mobile hoist. A device for hauling out small craftand moving them over land to cradles or to the placeat which their hulls and underwater appendagesare cleaned, painted, or repaired. It consists of aself-powered steel frame on rubber tires, with twoslings suspended from electric hoists. The lift isrun out onto a trackway extending over the water,the slings are lowered beneath the water, and theboat is positioned over the slings; the hoists thenraise the slings (and the boat) above the trackwayand ground, and the lift backs off the trackway.

Mole. A form of breakwater alongside which vesselsmay lie on the sheltered side only; in some cases itmay lie entirely within an artificial harbor, per-mitting vessels to lie along both sides. A structure,usually massive, on the seaward side of a harborfor its protection against current and wave action,drift ice, sanding up, wind, etc. Sometimes it maybe suitable for the berthing of ships. See also: Jetty;Quay.

Mooring. A place where a vessel may be secured.(Usually in pl.) The equipment used to secure avessel. The process of securing a vessel, other thananchoring with a single anchor.

Mooring buoy. A buoy secured to the bottom by per-


manent moorings and provided with means formooring a vessel by use of its anchor chain or moor-ing lines.

Morse code light. A light in which the appearancesof light of two clearly different durations are groupedto represent a character or characters in the Morsecode.

Moraine. Any accumulation of loose material depos-ited by a glacier.

Mound. A low hill of earth, natural or artificial; ingeneral, any prominent, more or less isolated hill.

Mount. A large hill or mountain, usually a detached,characteristically conical mass of earth.

Mountain. A natural elevation of the earth�s surfacerising more or less abruptly from the surroundinglevel, and attaining an altitude which, relatively toadjacent elevations, is impressive or notable.

Mountain range. A series of connected and alignedmountains or mountain ridges.

Mouth. The place of discharge of a stream into theocean or entrance to a bay from the ocean.

Mud. One of several descriptors of the �nature of theseabed� used in Chart No. 1. A general term ap-plied to mixtures of sediments in water. Where thegrains are less than 0.002 mm in diameter, themixture is called clay. Where the grains are be-tween 0.002 mm and 0.0625 mm in diameter themixture is called silt.

Muskeg. A bog or marsh. (Local in north centralUnited States, Canada, and Alaska.)

Narrows. A navigable narrow part of a bay, strait,river, etc.

National boundary. The seaward boundary of theUnited States within which it exercises exclusivesovereignty except for the right of innocent passageof foreign vessels; the three-mile limit. See: Mar-ginal sea.

National Oceanic and Atmospheric Administra-tion (NOAA). NOAA was formed on October 3,1970, by Reorganization Plan 4 of 1970. Its princi-pal functions are authorized by Title 15, Chapter 9,United States Code (National Weather Service); Title33, Chapter 17, United States Code (National OceanSurvey); and Title 16, Chapter 9, United States Code(National Marine Fisheries Service). NOAA�s mis-sion was further defined by the Coastal Zone Man-agement Act of 1972, the Marine Mammals Protec-tion Act of 1972, the Marine Protection, Research,

and Sanctuaries Act of 1972, the Weather Modifi-cation Reporting Act of 1972, the Endangered Spe-cies Act of 1973, the Offshore Shrimp Fisheries Actof 1973, and the Fishery Conservation and Man-agement Act of 1976. The mission of NOAA is toexplore, map, and chart the global ocean and itsliving resources, to manage, use, and conserve thoseresources and to describe, monitor, and predict con-ditions in the atmosphere, ocean, sun and spaceenvironment, issue warnings against impendingdestructive natural events, develop beneficial meth-ods of environmental modification, and assess theconsequences of inadvertent environmental modifi-cation over several scales of time.

Natural harbor. A harbor possessing natural shel-ter in a large degree. Natural harbors require onlythe provision of such facilities as quays or piers andsometimes deepening by artificial means to makethem serviceable as shipping ports.

Natural shoreline. This is the line of contact be-tween the surface of a body of water and naturalland, including islands. It does not include the waterline along floating or artificial features, or alongrocks smaller than those considered to be islands.

Nautical. Of or pertaining to ships, navigation (chieflymarine), or seamen. In contrast, navigational re-fers to navigation only, marine refers to the sea,maritime indicates relationship or proximity to thesea, and naval refers to the Navy.

Nautical chart. A representation of a portion of thenavigable waters of the earth and adjacent coastalareas on a specified map projection, and designedspecifically to meet requirements of marine navi-gation. Included on most nautical charts are: depthsof water, characteristics of the bottom, elevationsof selected topographic features, general configura-tion and characteristics of the coast, the shoreline(usually the mean high water line), dangers, ob-structions, aids to navigation, limited tidal data,and information about magnetic variation in thecharted area.

Nautical Chart Manual. A manual, published byNOAA, for the cartographer engaged in the con-struction and revision of nautical charts.

Navigability. The actual navigable capacity of awaterway and not the extent of tidal influence.

Navigable. Affording passage to a craft; capable ofbeing navigated.

Navigable waters of the United States. Navigablewaters of the United States are those waters that


are subject to the ebb and flow of the tide and/or arepresently used, or have been used in the past, ormay be susceptible for use to transport interstateor foreign commerce. A determination of naviga-bility, once made, applies laterally over the entiresurface of the waterbody, and is not extinguishedby later actions or events which impede or destroynavigable capacity. See 33 CFR Part 329 for a morecomplete definition of this term.

Navigation. The process of planning, recording, andcontrolling the movement of a craft or vehicle fromone place to another. The word �navigate� is fromthe Latin navigatus, the past participle of the verbnavigere, which is derived from the word navis,meaning �ship,� and agere, meaning �to move,� or�to direct.�

Navigational aid. An instrument, device, chart,method, etc., intended to assist in the navigation ofa craft. This expression should not be confused withaids to navigation, which refers only to devices ex-ternal to a craft. In British usage, the terms navi-gational aid and aid to navigation are used with-out distinction.

Navigation, coastwise. Navigation in the vicinityof a coast, in contrast with offshore navigation.

Navigation, electronic. Navigation by means of elec-tronic equipment. The expression electronic navi-gation is more inclusive than radio navigation, sinceit includes navigation involving any electronic de-vice or instrument.

Navigation, offshore. Navigation at distance froma coast, in contrast with coastwise navigation.

Navigation, radio. Any method of navigation inwhich location or velocity is inferred from measure-ments on radio waves. The term is generally ap-plied only to one of the following methods of naviga-tion: (a) measuring direction or distance to two ormore radio transmitters, (b) measuring differencesof distance to two or more pairs of radio transmit-ters, (c) measuring the Doppler shift in frequencyof a signal from an orbiting beacon or beacons.

Navigation system. A set of equipment and tech-niques by which the location of a moving vehicle,vessel, or aircraft can be determined and madeknown sufficiently quickly so the information canbe used for navigation.

Navigation system, hyperbolic. A navigation sys-tem using the differences in distance (measured inwavelengths) of a mobile unit from three or morefixed stations to determine location. The locus of

points all of which have the same difference of dis-tance is a �hyperbola.� If the difference in distancefrom two pairs of fixed points (one point of whichmay be common to the two) is determined, two in-tersecting hyperbolas result and the mobile unit islocated at one of those intersections.

Neatline. Line, usually grid or graticule, boundingthe detail of a map. Also referred to as �inner neat-line� to differentiate from border drawn outside ofneatline.

Neck. (1) A narrow isthmus, cape, or promontory. (2)The land areas between streams flowing into a soundor bay. (3) A narrow strip of land, which connects apeninsula with the mainland. (4) A narrow body ofwater between two larger bodies; a strait.

Net under keel clearance. The distance betweenthe ocean bottom and the portion of a tanker�s hullclosest to the ocean bottom when the tanker is un-derway, moored, or anchored, considering ship mo-tion in responding to the combination of actual wind,wave, tide, and current conditions.

New chart. A new chart is usually constructed tosatisfy the needs of navigation in a particular area;e.g., the area had no prior adequate chart coverageof the same scale, or limits are radically changed.The new chart may cancel an existing chart.

New editions. A chart issue that cancels a previousissue. If the new information renders that existingchart obsolete, the new printing is designated a newedition. A new edition reflects one or more changesof such importance to navigation that all previousprintings are obsolete. Changes may be based oncorrections from the Notice to Mariners (NM), inaddition to other sources. The date of a new editionis the date of the latest NIMA NM from which thechart has been corrected. The edition number anddate are printed in the lower left corner of the chart.

Nineteen-Year Tidal Cycle. The period of time gen-erally reckoned as constituting a full tidal cyclebecause the more important of the periodic tidalvariations due to astronomic causes will have passedthrough complete cycles. The longest cycle to whichthe tide is subject is due to a slow change in thedeclination of the moon, which covers 18.6 years.

Nominal range. The maximum distance a light maybe seen in clear weather (meteorological visibilityof 10-nautical miles) without regard to the curva-ture of the earth, height of eye, or height of light.Listed for all federal lighted aids except range lightsand directional lights.


Nontidal basin. An enclosed basin separated fromtidal waters by a caisson or flood gates. Ships aremoved into the dock near high tide. The dock isclosed when the tide begins to fall. If necessary,ships are kept afloat by pumping water into thedock to maintain the desired level. Also called wetdock.

Nontidal waters. Waters not subject to tidal influ-ence.

Normal pool elevation. The level at which a con-trolled body of water is generally maintained.

North. The primary reference direction relative to theearth; the direction indicated by 000° in any sys-tem other than relative. True north is the direc-tion of the north geographic pole; magnetic norththe direction north as determined by the earth�smagnetic compass; grid north an arbitrary refer-ence direction used with grid navigation.

Notch. A short defile through a hill, ridge, or moun-tain. A deep, close pass; a defile; gap. (Local inNew England.)

Notice to Mariners (NM). A weekly publication ofthe National Imagery and Mapping Agency (NIMA)prepared jointly with NOAA and the U.S. CoastGuard giving information on changes in aids to navi-gation (lights, buoys, daymarks, ranges), dangersto navigation (rocks, shoals, reefs, wrecks), selecteditems from the Local Notice to Mariners, impor-tant new soundings, changes in channels, harborconstruction, radionavigation information, new andrevised charts and publications, special warningsand notices, pertinent Hydrolant, Hydropac,Navarea IV and XII messages and in general, allsuch information as affects the mariner�s charts,manuals, catalogs, sailing directions (pilots), etc.The Notice to Mariners should be used routinelyfor updating the latest editions of nautical chartsand related publications.

Nun buoy. An unlighted buoy of which the upper-part of the body (above the water line), or the largerpart of the superstructure, has approximately theshape of a cone with vertex upwards. Called coni-cal buoy in British terminology.

Obscured. Said of the arc of a light sector designatedby its limiting bearings in which the light is notvisible from seaward.

Obsolete chart. A chart which is not considered safeto use for navigation because it does not contain thelatest important navigational information.

Obstruction. Anything that hinders or preventsmovement, particularly anything that endangersor prevents passage of a vessel or aircraft. The termis usually used to refer to an isolated danger to navi-gation, such as a submerged rock or pinnacle inthe case of marine navigation, and a tower, tall build-ing, mountain peak, etc., in the case of air naviga-tion.

Obstruction buoy. A buoy used alone to indicate adangerous reef or shoal. The buoy may be passedon either side.

Obstruction light. A light indicating a radio toweror other obstruction to aircraft.

Obstruction mark. A navigation mark used aloneto indicate a dangerous reef or shoal. The markmay be passed on either hand.

Occasional light. A light put into service only ondemand.

Ocean. The great body of salt water, which occupiestwo-thirds of the surface of the earth, or one of itsmajor subdivisions. The sea as opposed to the land.

Offshore. Away from the shore. The comparativelyflat zone of variable width which extends from theoutermark of the rather steeply sloping shorefaceto the edge of the continental shelf.

Offshore light stations. Manned light stations builton exposed marine sites to replace lightships.

Offshore navigation. Navigation at a distance froma coast, in contrast with coastwise navigation inthe vicinity of a coast.

Offshore tower. Manned or monitored light stationsbuilt on exposed marine sites to replace light ves-sels.

Offshore water. Water adjacent to land in whichthe physical properties are slightly influenced bycontinental conditions.

Off soundings. Said of a vessel navigating beyondthe 100-fathom curve. In earlier times, said of avessel in water deeper than could be sounded withthe sounding lead.

Off station. A floating aid not on its assigned posi-tion.

Omega Navigation System. A worldwide, continu-ous, radionavigation system of medium accuracy,which provides hyperbolic lines of position throughphase comparisons of VLF (10 kHz to 14 kHz) con-tinuous wave signals transmitted on a common fre-


quency on a time-shared basis. The system is com-prised of eight transmitting stations.

Omnirange. A radio aid to navigation providing di-rect indication of a magnetic bearing (omnibearing)of that station from any direction. Also called om-nidirectional range or omnidirectional beacon.

One-way traffic lane. A lane within which all shipsare advised to proceed in approximately the samedirection.

On soundings. Said of a vessel navigating withinthe 100-fathom curve. In earlier times, said of avessel in water sufficiently shallow for sounding bysounding lead.

Ooze. One of several descriptors of the �nature of theseabed� used in Chart No. 1. A soft, slimy, organicsediment covering part of the ocean bottom com-posed principally of shells or other hard parts ofminute organisms. Generally, ooze offers poor pur-chase for anchors.

Open coast. The coast that fringes the marginal seaas distinguished from the coast that fringes inlandwater. A coast that is not sheltered from the sea.

Open harbor. An unsheltered harbor exposed to thesea.

Open sea. The water area of the open coast seawardof the ordinary low-water mark, or seaward of in-land water.

Outer Continental Shelf (OCS). Means all sub-merged lands lying seaward and outside of the areaof �lands beneath navigable waters� as defined inSection 2(a) of the Submerged Lands Act (43 U.S.C.1301(a)) and of which the subsoil and seabed apper-tain to the United States and are subject to its ju-risdiction and control. �OCS activity� means anyoffshore activity associated with exploration for, ordevelopment or production of, the miners of the OCS.

Outer Continental Shelf (OCS) Facility. �OCSfacility� means any artificial island, installation,or other device permanently or temporarily attachedto the subsoil or seabed of the OCS, erected for thepurpose of exploring for, developing, or producingresources therefrom, or any such installation orother device (other than a ship or vessel) for thepurpose of transporting such resources. The termincludes mobile offshore drilling units when in con-tact with the seabed of the OCS for exploration orexploitation of subsea resources.

Outlet. The opening by or through which any body ofwater discharges its content.

Overfalls. Short, breaking waves, occurring when astrong current passes over a shoal or other subma-rine obstruction or meets a contrary current orwind. See: Rips.

Palisade. A picturesque, extended rock cliff risingsteeply from the margin of a stream or lake; a lineof bold cliffs, especially one showing basaltic col-umns (usually plural).

Parallels. Imaginary planes passing through theearth parallel to the equator and measure latitudesnorth or south of the equator.

Pass. (1) A navigable channel leading to a harbor orriver. Sometimes called Passage. (2) A break in amountain range, permitting earlier passage fromone side of the range to the other; also called Col.(3) A narrow opening through a barrier reef, atoll,or sand bar.

Passage. A narrow navigable channel, especially onethrough reefs or islands. Sometimes called a pass,or in New England waters, a hole.

Passing light. A term applies to a lower candlepowerlight mounted on a light structure. Used where amariner passes out of the main light beam (such asa range light) but still needs to keep the structurein sight during transit.

Peak. A pointed mountain summit; the topmost point;summit; a seamount rising more than 500 fathomsfrom the seafloor, and having a pointed or roundedtop.

Pebble. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. See under: Stones.

Pecked line. In cartography, a symbol consisting ofa line broken at regular intervals.

Peninsula. A body of land jutting into and nearlysurrounded by water, frequently (but not necessar-ily) connected to a larger body of land by a neck oristhmus.

Perch. A staff placed on top of a buoy, rock, or shoalas a mark for navigators. A ball or cage is some-times placed at the top of the perch, as an identify-ing mark.

Period. The interval of time between the commence-ment of the identical aspect in two successive cyclesof a rhythmic light.

Permafrost. A layer of soil or bedrock at a variabledepth beneath the surface of the earth in which thetemperature has been below freezing continuouslyfrom a few to several thousands of years.


Photogrammetry. (1) The science or art of obtain-ing reliable measurements from photographic im-ages. (2) The science of preparing charts and mapsfrom aerial photographs using stereoscopic equip-ment and methods.

Pictorial symbol. A symbol whose form is a simpli-fied portrayal of the feature or phenomenon it rep-resents.

Pier. (1) A structure extending into the water approxi-mately perpendicular to a shore or a bank and pro-viding berthing for ships, and which may also pro-vide cargo-handling facilities. See also: Wharf. (2)A structure extending into the water approximatelyperpendicular to a shore or bank and providing apromenade or place for other use, as a fishing pier.(3) A support for the spans of a bridge.

Pierhead. That part of a pier or jetty projecting far-thest into the water.

Pile. A long, heavy timber or section of steel, con-crete, etc., forced into the earth to serve as a sup-port, as for a pier, or to resist lateral pressure.

Pile, sheet. A pile with a generally slender flat cross-section to be driven into the ground or seabed andmeshed or interlocked with like members to form adiaphragm, wall, or bulkhead.

Piling. A group of piles set in a row.

Pillar buoy. A buoy composed of a tall central struc-ture mounted on a broad flat base. Also called bea-con buoy.

Pilot. One who directs the movements of a vesselthrough pilot waters; usually, one who has demon-strated extensive knowledge of channels, aids tonavigation, dangers to navigation, etc., in a par-ticular area and is licensed for that area.

Pilot area. A pilot area represents a meeting or board-ing place where vessels pick up or disembark pi-lots. A pilot vessel may either cruise in the areacontinuously or come out on request.

Pilot station. The office or headquarters of pilots;the place where the services of a pilot may be ob-tained.

Pinnacle. On the seafloor, a high tower or spire-shaped pillar of rock or coral, along or cresting asummit. It may or may not be a hazard to surfacenavigation. Due to the sheer rise from the seafloor,no warning is given by sounding.

Pipe. A hollow metal tube, of varying diameters and

lengths, imbedded in the bottom in a manner simi-lar to a pile. Pipes are often used as privately main-tained aids to navigation and in the determinationof beach or bottom sand migration (deposition orerosion).

Plain. A region of uniform general slope, compara-tively level, of considerable extent, and not brokenby marked elevations and depressions (it may bean extensive valley floor or a plateau summit); andextent of level or nearly level land; a flat, gentlysloping or nearly level region of the seafloor.

Plan position indicator (PPI). A cathode ray scopeon which signals appear in correct relation to eachother, so that the scope face presents a maplike rep-resentation of the area about the transmitter, thedirector of a target being represented by the direc-tion of its echo from a center and range by its dis-tance from that center.

Plateau. An elevated plain, tableland, or flat-toppedregion of considerable extent; a comparatively flat-topped elevation of the seafloor greater than 60-nau-tical miles across the summit and normally risingmore than 100 fathoms on all sides.

Platform. (1) In geographical literature, a natural orartificial terrace; a flat elevated piece of ground; atableland, a plateau. (2) In oceanographic termi-nology, any artificial structure (aircraft, ship, buoy,or tower) from or on which oceanographic instru-ments are suspended or installed. (3) Structureswhich are erected on or over the seabed and subsoilof the Outer Continental Shelf and in the watersunder the jurisdiction of the United States, for thepurpose of exploring for, developing, removing, andtransporting resources there from. This includesall fixed structures, temporary or permanent, forwhich a U.S Army Corps of Engineers� permit isissued. It includes, but is not necessarily limitedto, all drilling platforms, production platforms, quar-ters platforms, pipeline riser platforms, manifoldplatforms, loading platforms, boat landings, cais-sons, oil well protective structures, tank batterybarges submerged on station, drilling barges sub-merged on location, breakwater barges submergedon location, and all other piles, pile clusters, pipes,or structures erected in the waters.

Pocosin. A swamp; a dismal. (Southern U.S.)

Point. The extreme end of a cape, or the outer end ofany land area protruding into the water (less promi-nent than a cape).

Polyconic map projection. A map projection hav-ing the central geographic meridian represented by


a straight line, along which the spacing for linesrepresenting the geographic parallels is proportionalto the distances between the parallels; the parallelsare represented by arcs of circles which are not con-centric, but whose centers lie on the line represent-ing the central meridian, and whose radii are de-termined by the lengths of the elements of cones,which are tangent along the parallels. All merid-ians except the central ones are curved.

Pond. A small body of still water of artificial forma-tion, its bed being either hollowed out of the soil orformed by embanking and damming up a naturalhollow. A small fresh-water lake.

Pontoon. A flat-bottomed boat, or a number of flat-bottomed boats, or other floating objects, such ashollow cylinders, used as supports for a bridge.

Pontoon bridge. A bridge supported on pontoons.

Pool. A water hole or small pond; a small body ofstanding water; a small and rather deep body of(usually) fresh water, as one in a stream.

Port. A place for the loading and unloading of vesselsrecognized and supervised for maritime purposesby the public authorities. The term includes a cityor borough for the reception of mariners and mer-chants and therefore denotes something more thana harbor or hare. A port may possess a harbor, buta harbor is not necessarily a port. Any naturalcreek or inlet on the seashore with adequate depthof water and sufficient shelter for ships fulfills theessential conditions of a harbor. To make it a port,in the accepted sense of the word, there must be inaddition accommodation and facilities for landingpassengers and goods and some amount of overseastrade.

Port hand buoy. A buoy which is to be left to theport hand when approaching from the open sea orin general proceeding in the direction of the mainstream of flood current, or in the direction estab-lished by appropriate authority.

Position. A point defined by stated or implied coordi-nates, particularly one on the surface of the earth.A fix is a relatively accurate position determinedwithout reference to any former position. A run-ning fix is a position determined by crossing linesof position obtained at different times and advancedor retired to a common time. An estimated positionis determined from incomplete data or data of ques-tionable accuracy. A dead reckoning position isdetermined by advancing a previous position forcourses and distances. A most probable position isthat position of a craft judged to be most accurate

when an element of doubt exists as to the true posi-tion. It may be a fix, running fix, estimated posi-tion, or dead reckoning position depending upon theinformation which it is based. An assumed posi-tion is a point at which a craft is assumed to belocated. A geographical position is that point onthe earth at which a given celestial body is in thezenith at a specified time, or any position definedby means of its geographical coordinates. A geo-detic position is a point on the earth the coordinatesof which have been determined by triangulation froman accurately known initial station or one definedin terms of geodetic latitude and longitude. An as-tronomical position is a point on the earth whosecoordinates have been determined as a result of ob-servation of celestial bodies, or one defined in termsof astronomical latitude and longitude. A maritimeposition is the location of a seaport or other pointalong a coast. A relative position is one defined withreference to another position, either fixed or mov-ing.

Position approximate. Of inexact position. Theexpression is used principally on charts to indicatethat the position of a wreck, shoal, etc., has notbeen accurately determined or does not remain fixed.Usually shown by the abbreviation �PA�.

Position doubtful. Of uncertain position. The ex-pression is used principally on charts to indicatethat a wreck, shoal, etc., has been reported in vari-ous positions and not definitely determined in any.Usually shown by the abbreviation �PD�.

Position, estimated. The most probable position ofa craft determined from incomplete data or data ofquestionable accuracy. Such a position might bedetermined by applying a correction to the dead reck-oning position.

Positioning system, hyperbolic. A positioningsystem in which the observer measures the differ-ence in time of reception of signals from two sta-tions whose coordinates are known. The differencein time is converted to a difference in distance. Thelocus of all points lying at a fixed difference in dis-tance from two points are the two branches of ahyperbola.

Positioning system, inertial. A positioning sys-tem consisting of a computer and an assemblage ofthree accelerometers and two or three gyroscopes.The gyroscopes are fastened together in such a waythat they define the orientation of the accelerom-eters with respect to nonrotating coordinates andthe accelerometers measure the components of ac-celeration of the positioning system along the direc-


tions defined by the gyroscopes. The computer andassociated equipment integrate the components ofacceleration to give the three components of displace-ment of the positioning system.

Positioning system, radio. A positioning systemin which the travel time or phase shift of radio wavesis measured. The most common radio positioningsystems at present measure the difference in timeof travel of radio pulses from three or more knownpoints.

Positioning system, satellite. A positioning sys-tem consisting of a radio receiver, or receiver andtransmitter, at the point whose location is to bedetermined, one or more beacons or transpondersin orbit about the earth, and a computing systemfor determining and predicting the orbits. The sat-ellites can be considered points of known location.The radio receiver may measure times of travel ofradio pulses, directions to the satellites or the Dop-pler shift in the frequency of the radio waves emit-ted by the satellites.

Post. A small beacon, more substantial than a perch,used for marking channels. See also: Pile.

Potable water. Water suitable for drinking or cook-ing, from both health and aesthetics considerations.

Potable water intake (PWI). A structure designedfor the intake of drinking water. The intake is usu-ally elevated above the bottom, supported and pro-tected by a debris-screening structure (crib), a sepa-rately charted feature.

Pound net. A set net composed of vertical nettingsupported and held in place by stakes. It consistsof three essential parts. The pot (pound, pocket,bowl), the wings or hearts and the leader or lead.The pound consists of a bag of stout netting with 1-inch meshes the margin of which is supported byupright stakes. The bottom of the pound is spreadand secured by ropes which pass through loops nearthe lower end of the stakes. The wings or heart arevertical fences of netting diverging from the entranceof the net. The mesh is 1/2-inch and they are sup-ported by stakes. The leader, which may vary inlength from about 150 feet to 1,000 or more, ex-tends from shore or shallow water into deeper wa-ter and deflects the fish toward the heart or wings.

Prairie. A treeless and grassy plain; an extensivetract of grassland; a low, sandy, grassy tract in theFlorida pine woods.

Pratique. Permission granted by the quarantine au-thorities (U.S. Public Health Service) to a vessel,

which has arrived from a foreign port, to communi-cate with the shore; pratique is normally grantedonly after inspection and release. Pratique may begranted by radio without inspection to some of thelarger passenger vessels entering certain specifiedU.S. ports; a request for such radio pratique mustbe made by radio, giving all particulars regardingsanitary conditions aboard, from 12 to 24 hoursbefore the time of arrival at the port.

Precautionary area. A routing measure compris-ing an area within defined limits where ships mustnavigate with particular caution and within whichthe direction of traffic flow may be recommended.

Precipice. The brink or edge of a high and very steepcliff; an abrupt declivity.

Preliminary chart. A chart for which there is astrong requirement, but of a region where some orall of the survey data do not meet modern stan-dards. The deficiencies in surveys may be due tosmall-scale, outmoded, or nonstandard survey tech-niques, obsolete age, unprocessed or unapproveddata, or other factors which cause the survey datato be below customary standards for the scale of thechart.

Primary light. A major aid to navigation establishedfor the purpose of making landfalls and coastwisepassages from headland to headland or for mark-ing areas dangerous to mariners.

Prime meridian. The meridian of longitude 0°, usedas the origin for measurement of longitude. Themeridian of Greenwich, England, is almost univer-sally used for this purpose.

Private aids to navigation. In U.S. waters, thoseaids to navigation not established and maintainedby the U.S. Coast Guard. Private aids include thoseestablished by other federal agencies with prior U.S.Coast Guard approval, those aids to navigation onmarine structures or other works which the own-ers are legally obligated to establish, maintain, andoperate as prescribed by the U.S. Coast Guard, andthose aids which are merely desired, for one reasonor another, by the individual corporation, state orlocal government, or other body that has establishedthe aid with U.S. Coast Guard approval. Althoughprivate aids to navigation are inspected periodicallyby the U.S. Coast Guard, the mariner should exer-cise special caution when using them for generalnavigation.

Prohibited area. An area shown on nautical chartswithin which navigation and/or anchoring is pro-hibited except as authorized by appropriate author-


ity. See also: Danger area, Restricted area.

Projection. (1) The lines representing the parallelsof latitude and meridians of longitude drawn on asurvey sheet, map, or chart. (2) The representationof a figure on a surface, either plane or curved, ac-cording to a definite plan. In a perspective projec-tion this is done by means of projecting lines ema-nating from a single point, which may be infinity.

Projection, lambert conformal conic. A confor-mal projection of the conical type, on which all geo-graphic meridians are represented by straight lines,which meet in a common point outside the limits ofthe map, and the geographic parallels are repre-sented by a series of arcs of circles having this com-mon point for a center. Meridians and parallelsintersect at right angles, and angles on the earthare correctly represented on the projection.

Projection, mercator. A conformal projection of thecylindrical type. The equator is represented by astraight line true to scale; the geographic merid-ians are represented by parallel straight lines per-pendicular to the line representing the equator; theyare spaced according to their distance apart at theequator. The geographic parallels are representedby a second system of straight lines perpendicularto the family of lines representing the meridians,and therefore, parallel with the equator.Conformality is achieved by mathematical analy-sis, the spacing of the parallels being increased withthe increasing distance from the equator to conformwith the expanding scale along the parallels result-ing from the meridians being represented by paral-lel lines. Since rhumb lines appear as straight linesand directions can be measured directly, this pro-jection is widely used in navigation.

Projection, skewed. Any standard projection usedin map or chart construction, which does not con-form to a general north-south format with relationto the neatlines of the map or chart.

Promontory. High land extending into a large bodyof water beyond the line of the coast. Called head-land when the promontory is comparatively highand has a steep face. Also called foreland.

Proportional dividers. An instrument consistingin its simple form of two legs pointed at both endsand provided with an adjustable pivot, so that forany given pivot setting, the distance between oneset of pointed ends always bears the same ratio tothe distance between the other set. A change in thepivot changes the ratio. The dividers are used intransferring measurements between charts or other

drawings which are not at the same scale.

Protractor, three-arm. An instrument consistingessentially of a circle graduated in degrees, to whichis attached one fixed arm and two arms pivoted atthe center and provided with clamps so that theycan be set at any angle to the fixed arm, within thelimits of the instrument. It is used for finding aship�s position, when the angles between three-fixedand known points are measured.

Province. A region composed of a group of similarbathymetric features whose characteristics aremarkedly in contrast with those of surroundingareas.

Publisher�s note. A marginal note which indicatesthe publisher and usually place of publication.

Pumping platform complex (PPC). A single plat-form of a series of interconnected platforms thathave one or more of the following capabilities: (1)pumping oil between a vessel and the shore; (2)berthing and messing facilities for assigned person-nel; (3) landing area for helicopters; and (4) moor-ing and loading for small vessels.

Quartz. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. Quartz is crystal-line silica. In its most common form it is colorlessand transparent, but it takes a large variety of formsof varying degrees of opaqueness and color. It is themost common solid mineral. Part of the ocean bedis composed of quartz.

Quay. A structure of solid construction along a shoreor bank which provides berthing for ships and whichgenerally provides cargo-handling facilities. A simi-lar facility of open construction is called a wharf.See also: Mole.

Quicksand. Loose, yielding, wet sand which offersno support to heavy objects. The upward flow of thewater has a velocity that eliminates contact pres-sures between the sand grains and causes the sand-water mass to behave like a fluid.

Race. Swiftly flowing water in a narrow channel orriver; also the channel itself which may be artifi-cial as in a mill-race. Also a swift rush of waterthrough a narrow channel in tidal waters andcaused by the tidal movement of the waters. See:Tide race.

RACON (Radar Transponder Beacon). A radio�navigation system that transmits a coded signalwhich is displayed on the user�s radar screen allow-ing him to identify the aid and determine the aid�s


range and bearing.

Radar. An electronic system designed to transmitradio signals and receive reflected images of thosesignals from a �target� in order to determine thebearing and distance of the �target.�

Radar beacon. A radar transmitter whose emissionsenable a ship to determine its direction and frequentposition relative to the transmitter by means of theship�s radar equipment. There are two general typesof radar beacons. One type, the RACON, must betriggered by the ship�s radar emissions; the othertype, the RAMARK, transmits continuously andprovides bearings only.

Radar buoy. A buoy having corner reflectors designedinto the superstructure, the characteristic shape ofthe buoy being maintained. This is to differentiatefrom a buoy on which a corner reflector is mounted.

Radar dome. A dome-shaped structure used to pro-tect the antenna of a radar installation.

Radar reflector. A special fixture fitted to or incor-porated into the design of certain aids to navigationto enhance their ability to reflect radar energy. Ingeneral, these fixtures will materially improve theaids for use by vessels equipped with radar.

Radiobeacon. Electronic apparatus which transmitsa radio signal for use in providing a mariner a lineof position.

Radiobeacon characteristic. The description of thecomplete cycle of transmission of a radiobeacon in agiven period of time, inclusive of any silent period.

Radio direction finder (RDF). Radio receivingequipment which determines the direction of arrivalof a signal by measuring the orientation of the wavefront or of the magnetic or electric vector. Radiodirection finders may be either manual or auto-matic. Also called direction finder. Formerly calledradio compass.

Radio frequency. Any electromagnetic wave occur-ring within that segment of the spectrum normallyassociated with some form of radio propagation.Radio frequencies are usually classified as very low,3 to 30 kilohertz (kHz); low, 30 to 300 kHz; me-dium, 300 to 3,000 kHz; high, 30 to 30 megahertz;very high, 30 to 300 megahertz; ultra high, 300 to3,000 megahertz; super high, 3 to 30 gigahertz; ex-tremely high, 30 to 300 gigahertz.

Radio mast. A radio mast is a tall structure heldvertical by guylines.

Radionavigation. (1) The determination of position,or the obtaining of information relating to position,for the purposes of navigation by means of the propa-gation properties of radio waves. (2) As defined bythe International Telecommunication Union (ITU),radiodetermination used for the purposes of navi-gation, including obstruction warning.

Radio station. A place equipped with one or moretransmitters or receivers, or a combination of trans-mitters and receivers, including the accessoryequipment necessary at one location, for carryingon a radiocommunication service. Each station isclassified by the service in which it operates per-manently or temporarily.

Radio tower. A radio tower is a latticed structure,which is self-supporting.

Ramp. A sloping structure that can either be used asa landing place, at variable water levels, for smallvessels, landing ships, or a ferry boat, or for haul-ing a cradle carrying a vessel.

Range. (1) Two or more objects in line. Such objectsare said to be �in range.� An observer having themin range is said to be �on the range.� Two beaconsare frequently located for the specific purpose offorming a range to indicate a safe route or thecenterline of a channel. Called leading marks inBritish terminology. (2) Distance in a single direc-tion or along a great circle. (3) The extreme dis-tance at which an object or light can be seen is calledvisual range. (4) The extreme distance at which asignal can be detected or used. The maximum dis-tance at which reliable service is provided is calledoperating range. The spread of ranges in whichthere is an element of uncertainty of interpretationis called critical range. (5) The distance a craft cantravel at cruising speed without refueling is calledcruising radius. (6) The difference in extreme val-ues of variable quantity. See also: Range of tide.(7) A series of mountains or mountain ridges is calledmountain range. (8) A predetermined line alongwhich a craft moves while certain data are recordedby instruments usually placed below the line, orthe entire station at which such information is de-termined. See also: Degaussing range. (9) An areawhere practice firing of ordnance equipment is au-thorized. (10) On the seafloor, a series of ridges orseamounts.

Range, geographic(al). The greatest distance atwhich a light can be seen as a function of the cur-vature of the earth and heights of the light sourceand the observer.


Range, luminous. The greatest distance at which alight can be seen merely as a function of its lumi-nous intensity, the meteorological visibility, and thesensitivity of the observer�s eye.

Range, nominal. The luminous range of a light in ahomogeneous atmosphere in which the meteorologi-cal visibility is 10-sea miles.

Range of tide. The difference in height between con-secutive high- and low-tide waters. The mean rangeis the difference in the height between mean highwater and mean low water.

Rapid(s). Portions of a stream with accelerated cur-rent where it descends rapidly but without a breakin the slope of the bed sufficient to form a waterfall.Usually used in the plural.

Ravine. A gulch; a small gorge or canyon, the sidesof which have comparatively uniform slopes.

Reach. The comparatively straight segment of a riveror channel between two bends. That part of a wind-ing river between the last bend and the sea is calleda sea reach; that part between the harbor and thefirst bend is called a harbor reach.

Rebuilt. A fixed aid, previously destroyed, which hasbeen restored as an aid to navigation.

Reciprocal bearing. A bearing differing by 180° orone measured in the opposite direction, from a givenbearing.

Recommended direction of traffic flow. A trafficflow pattern indicating a recommended directionalmovement of traffic where it is impractical or un-necessary to adopt an established direction of traf-fic flow.

Recommended track. A route which has been spe-cially examined to ensure so far as possible that itis free of dangers and along which ships are ad-vised to navigate.

Reduction of soundings. Recorded soundings onhydrographic surveys are corrected for any depar-ture from true depths attributable to the method ofsounding or to a fault in the measuring apparatusand for the elevation of the tide or water level aboveor below the chart datum (tidal or stage correction).

Reef. A rocky or coral elevation dangerous to surfacenavigation which may or may not uncover at thesounding datum. A rocky reef is always detachedfrom shore; a coral reef may or may not be con-nected with the shore.

Reference datum. A general term applied to anydatum, plane, or surface used as a reference or base

from which other quantities can be measured.

Reference station. A tide or current station for whichindependent daily predictions are given in the TideTables and Tidal Current Tables, and from whichcorresponding predictions are obtained for subordi-nate stations by means of differences and ratios.See: Subordinate current station.

Register marks. Designated marks, such as smallcrosses, circles, or other patterns applied to origi-nal copy prior to reproduction to facilitate registra-tion of plates and to indicate the relative positionsof successive impressions. Also called: corner marks;corner ticks; register ticks; registration ticks; ticks.

Registration. Correct positioning of one componentof a composite map image in relation to the othercomponents. Achieved, for example, by punchingsets of holes, having a fixed horizontal relationshipto each other, in each component sheet and thenattaching the components together using speciallydesigned fasteners.

Relief. (1) The elevations or the inequalities, collec-tively of a land surface; represented on graphics bycontours, hypsometric tints, shading, spot eleva-tions, hachures, etc. Similar inequalities of theocean bed or their representation are called subma-rine relief. (2) The removal of a buoy from a stationand the providing of another buoy having the oper-ating characteristics authorized for that station.

Relighted. An extinguished aid returned to its ad-vertised light characteristics.

Relocated. Authorized movement of an aid from oneposition to another in the immediate vicinity.

Removable span bridge. A bridge with a portableor pontoon span that can be removed or drawn aside.

Repeatability. (1) A measure of the variation in theaccuracy of an instrument when identical tests aremade under fixed conditions. (2) In a navigation sys-tem, the measure of the accuracy with which thesystem permits the user to return to a specified pointas defined only in terms of the coordinates peculiarto that system.

Repeatable accuracy. In a navigation system, themeasure of the accuracy with which the systempermits the user to return to a position as definedonly in terms of the coordinates peculiar to thatsystem. For example, the distance specified for therepeatable accuracy of the system, such as LORAN-C is the distance between two LORAN-C positionsestablished using the same stations and time-dif-ference readings at different times. The correlation


between the geographical coordinates and the sys-tem coordinates may or may not be known.

Replaced. An aid previously off station, adrifts, ormissing restored by another aid of the same typeand characteristics.

Replaced (temporarily). An aid previously off sta-tion, adrift, or missing restored by another aid ofdifferent type and/or characteristic.

Representative fraction. The scale of a map or chartexpressed as a fraction or ratio that relates unitdistance on the map to distance measured in thesame unit on the ground. Also called natural scale,fractional scale.

Reprint. A reprinting of a chart without revision,necessitated by the depletion of stock. The issue isan exact duplicate of the current issue with nochanges in printing or publication dates.

Reset. A floating aid previously off station, adrift, ormissing returned to its assigned position (station).

Restricted area. A specified area designated by ap-propriate authority and shown on charts, withinwhich navigation is restricted in accordance withcertain specified conditions. See: Danger area;Prohibited area.

Restricted waters. Areas which for navigationalreasons such as the presence of shoals or other dan-gers confine the movements of shipping within nar-row limits.

Retractable bridge. A bridge with a movable spanthat can be withdrawn horizontally or within theremaining structure of the bridge.

Reversing current. A tidal current which flows al-ternately in approximately opposite direction witha slack water at each reversal of direction. Cur-rents of this type usually occur in rivers and straitswhere the direction of flow is more or less restrictedto certain channels.

Revetment. Facing of stone or other material, eitherpermanent or temporary, placed along the edge of astream to stabilize the bank and to protect it fromthe erosive action of the stream.

Revised print. A chart issue that does not cancel acurrent edition; the revisions are minor, the edi-tion number remains the same but the print dateis changed, and the chart is designated a revisedprint of that chart. The date of a revised print isshown to the right of the edition date.

Revision. The process of bringing the information ona map up to date. Continuous revision: a systemdesigned to keep the information on a map up todate at all times.

Revision cycle. The proposed time interval betweensuccessive revisions of a chart or map.

Rhythmic light. A light showing intermittently witha regular periodicity.

Ridge. A long and narrow elevation with steep sides;a long, narrow elevation of the seafloor, with steepsides and more irregular topography than a rise.

Right bank. That bank of a stream or river on theright of the observer when he is facing in the direc-tion of flow, or downstream. See also: Left bank.

Rincon. Corner or cove; an angular recess or hollowbend in a mountain, riverbank, cliff, or the like.(Local in Southwest) (Sp. origin)

Riparian boundaries. Water boundaries, or bound-aries formed by the sea or a river.

Riparian lands. Lands bordering on a river. Theterm �riparian� is also used as relating to the shoreof the sea or other tidal water, or of a lake or otherconsiderable body of water not having the charac-ter of a watercourse.

Rip current. A strong surface current flowing sea-ward from the shore. It usually appears as a visibleband of agitated water and is the return movementof water piled up on the shore by incoming wavesand wind. With the seaward movement concentratedin a limited band, its velocity is somewhat accentu-ated.

Riprap. A layer of broken rock, cobbles, boulders, orfragments of sufficient size and thickness to resistthe erosive forces of flowing water or wave action.Such structures usually are used to protect chan-nels with relatively high velocity flow, shores, slopes,slopes on dams, or outlets of structures.

Riprap mounds. Mounds of riprap maintained atcertain light structures to protect the structuresagainst ice damage and scouring action. Unchartedsubmerged portions present hazard to vessels at-tempting to pass extremely close aboard.

Rips. Agitation of water caused by the meeting ofcurrents or by a rapid current setting over an ir-regular bottom. Called tide rips when a tidal cur-rent is involved.

Rise. A long, broad elevation that rises gently andgenerally smoothly from the seafloor.


River. A natural stream of water, or greater volumethan a creek or rivulet, flowing in a more or lesspermanent bed or channel, between defined banksor walls, with a current which may either be con-tinuous in one direction or affected by the ebb andflow of the tidal current.

Road. An open anchorage affording less protection thana harbor. Some protection may be afforded by reefs,shoals, etc. Often used in the plural.

Rock. (1) An isolated rocky formation on a single largestone, usually one constituting a danger to naviga-tion. It may be always submerged, always uncov-ered, or alternately covered and uncovered by thetide. A pinnacle is a sharp-pointed rock rising fromthe bottom. (2) The naturally occurring materialthat forms the firm, hard, and solid masses of theocean floor. Also, rock is a collective term for massesof hard material generally not smaller than 256 mil-limeters.

Rock awash. In NOAA terminology, a rock exposedat any stage of the tide between the datum of meanhigh water and the sounding datum, or one justbare at these datums. For cartographic purposes,in order that the charted symbols may reflect themost probable condition of the rock as seen by themariner, rocks the summits of which are in thezone between 1 foot above mean high water and 1foot below the sounding datum on the Atlantic andgulf coasts and 2 feet on the Pacific coast are shownas rocks awash.

A rock that becomes exposed, or nearly so, betweenchart sounding datum and mean high water. Inthe Great Lakes, the rock awash symbol is used oncharts for rocks that are awash, or nearly so, atlow-water datum.

Rotary current. A tidal current that flows continu-ally with the direction of flow changing through allpoints of the compass during the tidal period.

Roundabout. A routing measure comprising a sepa-ration point or circular separation zone and a cir-cular traffic lane within defined limits. Traffic withinthe roundabout is separated by moving in a coun-terclockwise direction around the separation pointor zone. A circular area within definite limits inwhich traffic moves in a counterclockwise directionaround a specified point or zone.

Route charts. These NOAA charts are published ina single long, narrow sheet, printed front and backand folded. They are designed for river and narrowwaterway coverage, and for much of the IntracoastalWaterways. Most are issued in a protective card-

board jacket.

Routing. A complex of measures concerning routesaimed at reducing the risk of casualties; it includestraffic separation schemes, two-way routes, tracks,areas to be avoided, inshore traffic zones, and deep-water routes.

Routing system. Any system of one or more routesand/or routing measures aimed at reducing the riskof casualties; it includes traffic separation schemes,two-way routes, recommended tracks, areas to beavoided, inshore traffic zones, roundabouts, precau-tionary areas, and deep-water routes.

Ruin. A structure in decayed or deteriorated condi-tion resulting from neglect or disuse, or a damagedstructure in need of repair. A ruin is consideredhazardous if it extends over or into navigable wa-ters and thus represents a danger to surface navi-gation.

Rules of the road. The International Regulationsfor Preventing Collisions at Sea, commonly calledInland Rules of the Road, and Inland Rules of theRoad to be followed by all vessels while navigatingupon certain inland waters of the United States.Also called Rules of Navigation.

Saddle. A low point on a ridge or crestline; a ridgeconnecting two higher elevations; a low point on aridge or between seamounts.

Safety lanes. Specified sea lanes designated for usein transit by submarines and surface ships to pre-vent attack by friendly forces.

Safety zones. Established around Outer Continen-tal Shelf (OCS) facilities being constructed, main-tained, or operated on the OCS to promote the safetyof life and property on the facilities, their appurte-nances and attending vessels, and on the adjacentwaters within the safety zones.

Sailing charts. These NOAA charts are publishedat a scale smaller than 1:600,000, and are intendedfor planning and for fixing the mariner�s positionas the coast is approached from the open ocean orfor sailing along the coast between distant ports.The shoreline and topography are generalized andonly offshore soundings, principal navigationallights and buoys, and landmarks visible at consid-erable distances are shown.

Salt marsh. Flat, poorly drained coastal swampswhich are flooded by most high tides.

Salt pans. Shallow pools of brackish water used for


the natural evaporation of sea water to obtain salt.

Sanctuary, marine. Area established under provi-sions of the Marine Protection, Research, and Sanc-tuaries Act of 1972, Public law 92-532 (86 Stat.1052), for the preservation and restoration of itsconservation, recreational, ecological, or estheticvalues. Such an area may lie in ocean waters as farseaward as the outer edge of the Continental Shelf,in coastal waters where the tide ebbs and flows, orin the Great Lakes and connecting waters, and maybe classified as a habitat, species research, recre-ations and esthetic, or unique area.

Sand. One of several descriptors of the �nature of theseabed� used in Chart No. 1. Sediment consistingof small but easily distinguishable separate grainsbetween 0.0625 and 2 mm in diameter. It is calledvery fine sand if the grains are between 0.0625 mmand 0.125 mm in diameter, fine sand if between0.125 mm and 0.25 mm in diameter, medium sandif between 0.25 mm and 0.5 mm in diameter, coarsesand if between 0.50 mm and 1.0 mm in diameter,and very coarse sand if between 1.0 mm and 2.0mm in diameter. See also: Mud, Stones, Rock,Boulder.

Sandwave. A large wavelike sediment feature in veryshallow water and composed of sand. The wave-length may reach 100 meters; the amplitude isabout 0.5 meter. Also called megaripple.

Scale. The relationship between a linear dimensionon a chart and the actual dimension represented isexpressed, usually, as a ratio. Thus, the ratio1:10,000 or 1/10,000 means that one unit of mea-sure on the chart represents 10,000 of the sameunit on the surface of the earth. Just as 1:4 or 1/4 islarger than 1:8 or 1/8, a 1:40,000 scale chart is largerthan 1:80,000-scale chart. Consequently, a large-scale chart will show chart features in more detailbut will cover a smaller area; a smaller scale chartwill be more generalized but will cover a larger area.

Scale, bar. A graduated line on a map, plan, photo-graph, or mosaic, by means of which actual grounddistances may be determined. Also called graphicscale or linear scale.

Scale, border. A scale drawn along the border of achart.

Scale, large. A scale involving a relatively small re-duction in size. A large-scale chart is one coveringa small area. The opposite is small scale.

Scale, logarithmic. A scale graduated in the loga-rithms of uniformly spaced consecutive numbers.

Scale, small. A scale involving a relatively large re-duction in size. A small-scale chart is one coveringa large area. The opposite is large scale.

Scarp. A steep slope extending over a considerabledistance and marking the edge of a terrace, pla-teau, bench, etc.

Scarp, beach. An almost vertical slope along the beachcaused by erosion of wave action. It may vary inheight from a few inches to several feet, dependingon wave action and the nature and composition ofthe beach.

Schist. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. Schist is a foliatedcrystalline metamorphic rock composed of layers ofdifferent minerals that splits into thin irregularplates. Schist offers variable holding quality.

Scouring basin. A basin in which a quantity of wa-ter is impounded during the flood tide and the con-tents retained until a suitable time, about low wa-ter, when the gates are opened again and a volumeof water is let out to maintain desired depth of theentrance channel by scouring the bottom. Also calledsluicing pond.

Sea. (1) A body of salt water more or less confined bycontinuous land or chains of islands and forming aregion distinct from the great masses of water. (2)A body of water nearly or completely surrounded byland, especially if very large or composed of saltwater. Sometimes called inland sea. (3) Ocean ar-eas in general, including major indentations in thecoastline, such as gulfs. (4) Waves generated or sus-tained by winds within their fetch as opposed toswell. (5) The character of a water surface, particu-larly the height, length (period), and direction oftravel of waves generated locally.

Seaboard. The region of land bordering the sea. Theterms seaboard, coast, and littoral have nearly thesame meanings. Seaboard is a general term usedsomewhat loosely to indicate a rather extensive re-gion bordering the sea. Coast is the region of indefi-nite width that extends from the sea inland to thefirst major change in terrain features. Littoral ap-plies more specifically to the various parts of a re-gion bordering the sea, including the coast, fore-shore, backshore, beach, etc.

Sea buoy. The outermost buoy marking the entranceto a channel or harbor. Called landfall buoy in Brit-ish terminology.

Sea gate. (1) A way giving access to the sea such as agate, channel, or beach. (2) A gate which serves toprotect a harbor or tidal basin from the sea, such


as one of a pair of supplementary gates at the en-trance to a tidal basin exposed to the sea.

Sea mile. An approximate mean value of the nauti-cal mile equal to 6,080 feet, or the length of a minuteof arc along the meridian at latitude 48°. (Britishterminology: The length of one minute of arc, mea-sured along the meridian in the latitude of the posi-tion; its length varies both with the latitude andwith the figure of the earth in use.)

Sea wall. A structure separating land and water ar-eas, primarily designed to prevent erosion and otherdamage due to wave action. See also: Bulkhead.

Seaward. Away from the land; toward the sea.

Seaward boundary. Limits of any area or zone off-shore from the mean low, or mean lower low waterline and established by an act of the U.S. Congress,or agreed to by treaty. See: Mean low water line.

Seaweed. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. Seaweed includesany of a large variety of weeds generally found inshallow waters. Seaweed has no holding power;anchors must pass through the weed to grip theunderlying seabed. Anchors suitable for seaweedrequire a long, narrow fluke that penetrates deeplyto reach the bottom. Care must be taken in anchor-ing in seaweed to ensure that the anchor penetratesto the bottom. Searching for an alternative locationis often preferable to attempting to anchor in sea-weed.

Secondary light. A major light, other than a pri-mary seacoast light, established at harbor entrancesand other locations where high intensity and reli-ability are required.

Security zone. All areas of land, water, or land andwater, which are so designated by the Captain ofthe Port for such time as he deems necessary toprevent damage or injury to any vessel or water-front facility, to safeguard ports, harbors, territo-ries, or waters of the United States or to secure theobservance of the rights and obligations of the U.S.

Sediment(s), bottom. In general all sedimentarymaterial regardless of origin found on or in the sub-marine bottom, including ballast or other materialdumped into the sea by man. More specifically it islimited to unconsolidated mineral and organic ma-terial forming the sea bottom, not including coralreefs or bedrocks.

Seiche. A stationary wave usually caused by strongwinds and/or changes in barometric pressure. It isfound in lakes, semienclosed bodies of water, and in

areas of the open ocean.

Semidiurnal. Having a period or cycle of approxi-mately one-half of a tidal day. The predominant typeof tide throughout the world is semidiurnal, withtwo high waters and two low waters each tidal day.The tidal current is said to be semidiurnal whenthere are two flood and two ebb periods each day.

Separation zone or line. A zone or line separatingtraffic proceeding in one direction from traffic pro-ceeding in another direction. A separation zone mayalso be used to separate a traffic lane from the adja-cent inshore traffic zone.

Setting a buoy. The act of placing a buoy on assignedposition in the water.

Sewage. Human body wastes and the wastes fromtoilets and other receptacles intended to receive orretain body waste.

Shallow water. Commonly, water of such a depththat surface waves are noticeably affected by bot-tom topography. It is customary to consider waterof depths less than half the surface wavelength asshallow water.

Shelf: Continental; Insular; Island. A zone adja-cent to a continent (or around an island) and ex-tending from the low-water line to a depth at whichthere is usually a marked increase of slope towardoceanic depths.

Shelf edge. A line along which there is a marked in-crease of slope at the outer margin of a continentalshelf or an island shelf. (For charting purposes the100-fathom depth contour is normally accepted asthe shelf edge; the actual depth usually is less, butmay be more.)

Shingle. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. See under: Stones.

Shipping lane. A term used to indicate the generalflow of merchant shipping between two departure/terminal areas.

Ships� Routing. A publication of the InternationalMaritime Organization (IMO), which describes thegeneral provisions of ships� routing, traffic separa-tion schemes, deep-water routes, and areas to beavoided, which have been adopted by IMO. All de-tails of routing systems are promulgated throughNotices to Mariners, together with their dates ofimplementation. Also details of routing system aredepicted on charts and are given in Sailing Direc-tions.

Shoal. (1) Shallow. (2) An offshore hazard to naviga-


tion on which there is a depth of 10 fathoms or 20meters or less, composed of unsolidated material,except coral or rock. See: Reef.

Shoaling. A bottom effect, which describes the heightof the waves, but not the direction. It can be dividedinto parts which occur simultaneously. The one parthas to do with the fact that waves become less dis-persive close to shore; therefore, since the sameenergy can be carried by high waves of lesser height,this effect causes a gradual decrease in the waveheight. In the other part, the waves slow down, thecrests move closer together, and since the energybetween crests remain relatively fixed, the wavescan become higher near shore. These effects areevidenced in the initial decrease in height of theincoming wave, then an increase in height as thewave comes into shore.

Shore. That part of the land in immediate contactwith a body of water including the area betweenhigh- and low-water lines. The term shore is usu-ally used with reference to the body of water andcoast with reference to the land, as the east coast ofthe United States is part of the western shore of theAtlantic Ocean. The term shore usually refers to anarrow strip of land in immediate contact with anybody of water, while coast refers to a general regionin proximity to the sea. A shore bordering the seamay be called a seashore. See also: Foreshore;Backshore.

Shoreface. The narrow zone seaward from the lowtide shoreline, permanently covered by water, overwhich the beach sands and gravels actively oscil-late with changing wave conditions.

Shoreline. The line of contact between the land anda body of water. On NOAA nautical charts and sur-veys, the shoreline approximates the meanhighwater line. In NOAA usage, the term is con-sidered synonymous with �coastline.� See: Meanhigh water line.

Short-range systems. Those radionavigation sys-tems limited in their positioning capability to coastalregions, or those systems limited to making land-falls. Radar and radio direction finder are examples.

Significant. A condition or situation that could havea material consequence for the chart user A signifi-cant error, for example, could lead to an erroneous,even dangerous use of the chart.

Sill. On the seafloor the low part of a gap or saddleseparating basins. See also: Dock sill.

Sill depth. The greatest depth over a sill.

Silt. One of several descriptors of the �nature of theseabed� used in Chart No. 1. See under: Stones.

Single station range light. A direction light boundedby other sectors of different characteristics whichdefine its margins with small angles of uncertainty.Most commonly the bounding sectors are of differ-ent colors (red and green).

Sink, sinkhole. A depression which has subsurfacedrainage only, through natural holes and cavernsin limestone or by seepage into a lower lying watertable.

Skeleton tower. A tower, usually of steel, constructedof heavy corner members and various horizontaland diagonal bracing members.

Slack water (slack). The state of a tidal current whenits speed is near zero, especially the moment whena reversing current changes direction and its speedis zero.

Slip. A berthing space between two piers. Also calleddock.

Slipway. A structure in a shipyard on which vesselsare constructed so that when finished they may beslid into the water.

Slope. On the seafloor, the slope seaward from theshelf edge to the beginning of a continental or insu-lar rise or the point where there is a general reduc-tion in slope.

Slough. A minor marshland or tidal waterway whichusually connects other tidal areas; often more orless equivalent to a bayou.

Sluice. Sliding gate or other contrivance for chang-ing the level of a body of water by controlling flowinto or out of it.

Small-craft nautical charts. These charts are pub-lished by NOAA at scales from 1:10,000 to 1:80,000and are designed for easy reference and plotting inlimited spaces. In some areas these charts repre-sent the only chart coverage for all marine users.They portray regular nautical chart detail and otherspecific details of special interest to small-craft op-erators, such as enlargements of harbors; tide, cur-rent, and weather data; rules-of-the-road informa-tion; locations of marine facilities; anchorages;courses; and distances.

Snag. A tree or branch embedded in a river or lakebottom and not visible on the surface, formingthereby a hazard to boats.

Sound. A relative long arm of the sea or ocean form-


ing a channel between an island and a mainland orconnecting two larger bodies of water, as a sea andthe ocean, or two parts of the same body but usu-ally wider and more extensive than strait. The termhas been applied to many features which do not fitthe accepted definition. Many are very large bodiesof water, such as Mississippi Sound and PrinceWilliam Sound, others are mere salt water pondsor small passages between islands.

Sound buoy. A buoy equipped with either a gong,bell, whistle, or electronic horn. Bells and gongs onbuoys are sounded by tappers that hang from thetower and swing as the buoys roll in the sea. Bellbuoys produce a sound of only one tone; gong buoysproduce several tones. Whistle buoys make a loudmoaning sound caused by the rising and falling mo-tions of the buoy in the sea. A buoy equipped withan electronic horn, a horn buoy, will produce a puretone at regular intervals and will operate continu-ously regardless of the sea state.

Sounding. Measured or charted depth of water, orthe measurement of such depth. A no-bottom sound-ing is one in which the bottom is not reached. Avessel is said to be on soundings when it is navigat-ing primarily by means of the information obtainedby successive measurements of the depth of thewater, or is in an area where this can be done. Inother areas a vessel is said to be �off soundings.�

Sounding, danger. A minimum sounding chosen fora vessel of specific draft in a given area to indicatethe limit of safe navigation.

Sounding, doubtful. A depth shown on a chart overa shoal, a rock, etc., that may be less than thatindicated.

Sound signal. A sound transmitted in order to con-vey information as a fog signal. The term soundsignal is sometimes used to describe the apparatusgenerating the sound.

Special-purpose buoy. A buoy having no lateralsignificance used to indicate a special meaning tothe mariner which must be determined from ap-propriate nautical documents.

Spheroid. An ellipsoid; a figure resembling a sphere.Also called ellipsoid or ellipsoid of revolution, fromthe fact that it can be formed by revolving an el-lipse about one of its axes. If the shorter axis isused as the axis of revolution, an oblate spheroidresults, and if the longer axis is used, a prolatespheroid results. The earth is approximately anoblate spheroid.

Spire. A label on a nautical chart which indicates apointed structure extending above a building. Thespire is seldom less than two-thirds of the entireheight and its lines are rarely broken by stages orother features. The term is not applied to a shortpyramid-shaped structure rising from a tower orbelfry.

Spit. A small tongue of land or a narrow shoal (usu-ally sand) extending from the shore into a body ofwater. Generally the tongue of land continues in along narrow shoal for some distance from the shore.

Spoil. Mud, sand, silt or other deposits obtained fromthe bottom of a channel of harbor by dredging.

Spoil area. Area for the purpose of depositing dredgedmaterial, usually near and parallel to dredged chan-nels. Spoil areas are usually a hazard to navigationand navigators of even the smallest craft shouldavoid crossing these areas. Spoil areas are shownon nautical charts. See also: Dumping ground;Dump site. Also called spoil ground.

Spoil banks. Submerged accumulations of dumpedmaterial dredged from channels or harbors.

Spoil ground. See: Spoil area.

Spot elevation. A point on a map or chart whoseheight above a specified datum is noted, usually bya dot or a small sawbuck and elevation value.

Spring. A place where water issues naturally fromthe rock or soil upon the land or into a body of sur-face water.

Spring tides or tidal currents. Tides of increasedrange or tidal currents of increased speed occur-ring semimonthly as the result of the moon beingnew or full.

Spur. A subordinate elevation, ridge, or rise project-ing outward from a larger feature.

Stack. A label on a nautical chart which indicates atall smokestack or chimney. The term is used whenthe stack is more prominent as a landmark thanthe accompanying buildings.

Stake. An elongated wood or metal pole embedded inthe bottom to serve as a marker or support for fishnets.

Stand of tide. Sometimes called a platform tide. Aninterval at high or low water when there is no sen-sible change in the height of the tide.

Standpipe. A label on a nautical chart which indi-


cates a tall cylindrical structure, in a waterworkssystem, the height of which is several times thediameter.

Starboard. The right side of a craft, facing forward.The opposite is port.

Station buoy. An unlighted buoy set near a lightshipor an important buoy as a reference point shouldthe primary aid be moved from its assigned posi-tion.

Station, reference. A place where tide or tidal cur-rent constants have been determined from observa-tions, and which is used as a standard for the com-parison of simultaneous observations at a subordi-nate station. It is also a place for which indepen-dent daily predictions are given in the tide or tidalcurrent tables, from which corresponding predic-tions are obtained for other locations by means ofdifferences or factors. Also called standard stationand standard port (British terminology).

Stones. One of several descriptors of the �nature ofthe seabed� used in Chart No. 1. A general term forrock fragments ranging in size from 2 mm to 256mm. An individual stone is called a cobble if be-tween 64 mm and 256 mm, a pebble if between 4mm and 64 mm, and gravel if between 2 mm and 4mm. An aggregate of stones ranging from 16 mmto 256 mm is called shingle.

Strait. A relatively narrow waterway, usually nar-rower and less extensive than a sound, connectingtwo larger bodies of water.

Stranded and sunken. These terms apply exclusivelyto items that once possessed the ability to float butwhich are now resting on the bottom. Stranded itemsproject above the sounding datum. Sunken itemsdo not project above the sounding datum. Theseterms apply most often to wrecks. Masts, funnels,and other extensions of wreck superstructure shouldbe disregarded when applying the above definitions;these features may be above the sounding datumand still have the wreck classified as �sunken.�

Stranding. The destruction or loss of a vessel by itsbeing sunk or broken up by the violence of the seaor by its striking or stranding upon a rock, shoal,or the like. The term �stranding� refers most par-ticularly to the driving or running aground of avessel. It may be either accidental or voluntary.Voluntary stranding takes place where the ship isrun aground either to avoid a more serious fate, orfor some fraudulent purpose. In marine insurance,

a �touch-and-go� is not considered a stranding. Inorder to constitute a stranding, the ship must bestationary for a certain length of time.

Stream. Any river, brook, rivulet, or course of run-ning water. A steady current in the sea or in a river,especially the middle or most rapid part of a tide orcurrent.

Stream channel. The bed where a natural stream ofwater runs; the trench or depression washed in thesurface of the earth by running water; a wash, ar-royo, or coulee.

Strobe light. Many charted features marked withultrabright flashing lights of extremely short dura-tion. These bright flashes are produced by a strobelight device usually a xenon gas condenser-dischargeflash lamp or flash tube. Xenon flash tubes areunique light sources capable of firing extremelypower flash. The flash is almost similar to the spec-tral distribution of light of the sun, which rangesfrom ultraviolet to infrared regions. The durationof the flash is controlled from some microsecondsup to scores of milliseconds. Strobe lights are usedon certain U.S. Coast Guard maintained aids tonavigation and on potential aero hazards such asstacks, towers, and builds. The terms �Flick� and�Flash Tube� as used in U.S. Coast Guard Noticeto Mariners are considered to have strobe light char-acteristics for the purpose of nautical chart label-ing. Aids published in Notice to Mariners and LightLists as well as landmarks with the above charac-teristics are identified on nautical charts with thelabel �Strobe� incorporated within the label of theparticular feature.

Structure. The term �structure� includes, withoutlimitation, any pier, wharf, dolphin, weir, boom,breakwater, bulkhead, revetment, riprap, jetty,permanent mooring structure, power transmissionline, permanently moored floating vessel, piling, aidto navigation, or any other obstacle or obstruction.

Submarine cable. An insulated, waterproofed wireor bundle of wires for carrying an electric currentunder water. Such a cable is placed on or near thebottom.

Submarine valley (also called Seavalley). A de-pression in the sea bottom of broad valley form with-out the steep side slopes which characterize a can-yon.

Submerged. Under water; not showing above water.The opposite is �uncovered.�

Submerged lands. Lands covered by water at any


stage of the tide, as distinguished from tidelandswhich are attached to the mainland or an islandand cover and uncover with the tide. Tidelands pre-suppose a high-water line as the upper boundary,submerged lands do not.

Submerged production well. An oil or gas well thatis a seabed installation only, i.e., the installationdoes not include a permanent production platform.

Submerged rock. A rock covered at the chart sound-ing datum and considered to be potentially danger-ous to navigate. See also: Bare rock; Rock awash.

Subordinate current station. (1) A current sta-tion from which a relatively short series of observa-tions is reduced by comparison with simultaneousobservations from a control current station. (2) Astation listed in the Tidal Current Tables for whichpredictions are to be obtained by means of differ-ences and ratios applied to the full predictions at areference station. See: Reference station.

Summit. The highest point, part of elevation; top orapex.

Sunken rock. A rock potentially dangerous to sur-face navigation, the summit of which is below thelower limit of the zone for a rock awash.

Super-buoy. A very large buoy, generally more than5 meters in diameter. Its large size renders a su-per-buoy a potential hazard even to large vessels.The three principal types of super-buoy are: largenavigational buoy, offshore tanker loading/dischargebuoy (or single-point mooring), and the oceano-graphic data acquisition system (ODAS) buoy.

Survey, wire-drag. A hydrographic survey madeutilizing a wire drag. In areas of rocky bottom orwhere submerged obstacles such as wrecks arepresent, a wire-drag survey represents the mostpractical way of making sure that all obstructionsor dangers have been found and least depths overthem obtained. Also called wire-drag sweep.

Suspension bridge. A bridge suspended from chainsor cables which are anchored at either end and sup-ported by towers at regular intervals.

Swamp. A track of stillwater abounding in certainspecies of trees and course grass or boggy protuber-ances; a track of wet, spongy land, saturated, butnot usually covered with water; a boggy marshlandand stream; a slough.

Swash. A narrow channel or sound within a sandbank, or between a sand bank and the shore. Also

called swashway. A bar over which the sea washes.The rush of water up onto a beach following thebreaking of a wave.

Swash channel. (1) On the open shore, a channelcut by flowing water in its return to the parent body(e.g., a rip channel). (2) A secondary channel pass-ing through or shoreward of an inlet or river bar.

Sweep. To drag. Drag and sweep have nearly the samemeanings. Drag refers particularly to the locationof obstructions, or the making sure that obstruc-tions do not exist. Sweep may include, additionally,the removal of any obstruction located.

Sweeping. The process of towing a line or object be-low the surface, to determine whether an area isfree from isolated submerged dangers to vessels andto determine the position of any such dangers thatexist, or to determine the least depth of an area.The process of clearing an area or channel of minesor other dangers to navigation.

Swing bridge. A bridge that can be swung in a hori-zontal plane to allow tall vessels to pass.

Tableknoll. A seamount rising less than 500 fath-oms from the seafloor and having a comparativelysmooth, flat top with minor irregularities.

Tablemount. A seamount rising more than 500 fath-oms from seafloor and having a comparativelysmooth, flat top with minor irregularities.

Terrace. On the seafloor, a relatively flat, horizontalor gently inclined surface, sometimes long and nar-row, which is bounded by a steeper ascending slopeon one side and by a steeper descending slope on theopposite side.

Territorial sea (also called Marginal sea, [Adja-cent sea,] Marine belt, Maritime belt, and Three-mile limit). The water area bordering a nation overwhich it has exclusive jurisdiction, except for theright of innocent passage of foreign vessels. It is acreation of international law, although no agree-ment has thus far been reached by the internationalcommunity regarding its width. It extends seawardfrom the low-water mark along a straight coast andfrom the seaward limits of inland waters where thereare embayments. The United States has tradition-ally claimed 3-nautical miles as its width and hasnot recognized the claims of other countries to awider belt.

Territorial waters. Includes the territorial sea (mar-ginal sea) and the inland waters of a country (lakes,rivers, bays, etc.). Sometimes used as synonymous


with Territorial sea.

Thorofare. This shortened form of thoroughfare hasbecome standard for a natural waterway in marshyareas. It is the same type of feature as a slough orbayou.

Three-arm protractor. An instrument consistingessentially of a circle graduated in degrees, to whichis attached one fixed arm and two arms pivoted atthe center and provided with clamps so that theycan be set at any angle to the fixed arm, within thelimits of the instrument. It is used for finding aship�s position when the angles between three fixedand known points are measured. Also called sta-tion pointer.

Tidal basin. A basin without a caisson or gate inwhich the level of water rises and falls with thetides. Also called open basin. See also: Tidal har-bor; Nontidal basin.

Tidal current. A horizontal movement of the watercaused by gravitational interactions between thesun, moon, and earth.

Tidal current chart diagrams. A series of 12monthly diagrams to be used with the Tidal Cur-rent Charts. Each diagram contains lines that in-dicate the specific tidal current chart of each seriesto use, and speed factor to apply to that chart.

Tidal current charts. (1) Charts on which tidal cur-rent data are depicted graphically. (2) Tidal cur-rent chart; as published by NOAA, part of a set of12 charts which depict, by means of arrows andfigures, the direction and velocity of the tidal cur-rent for each hour of the tidal cycle.

Tidal Current Tables. (1) Tables which give the pre-dicted times of slack water and the predicted timesand velocities of maximum current flood and ebbfor each day of the year at a number of referencestations, together with time differences and veloc-ity ratios for obtaining predictions at subordinatestations. (2) Tidal Current Tables; published annu-ally in two volumes; Atlantic Coast of NorthAmerica; Pacific coast of North America and Asia.

Tidal cycle. A complete set of tidal conditions as thoseoccurring during a tidal day, lunar month, orMetonic cycle.

Tidal datum. Specific tide levels which are used assurfaces of reference for depth measurements in thesea and as a base for the determination of elevationon land. Many different datums have been used,particularly for leveling operations. Also called tidal

datum plane.

Tidal flat. A marsh or sandy or muddy coastal flatlandwhich is covered and uncovered by the rise and fallof the tide.

Tidal harbor. A harbor affected by the tides, in dis-tinction from a harbor in which the water level ismaintained by caissons or gates. See also: Nontidalbasin.

Tidal waters. All waters which flow and reflow un-der the influence of the tides. Arms of the sea, bays,creeks, coves, or rivers in which the tide ebbs andflows are properly denominated tidal waters. Theterm tidal water is not limited to water which issalt, but embraces also so much of the water of freshrivers as is propelled backward by the ingress andpressure of the tide. Also called tide waters.

Tide. The periodic rise and fall of the water resultingfrom gravitational interactions between the sun,moon, and earth. The vertical component of theparticulate motion of a tidal wave.

Tide lock. A lock situated between a basin or canaland tidewater to maintain the water at a desiredlevel as the height of the tide changes. Also calledguard lock.

Tide race. A very rapid tidal current through a com-paratively narrow channel. Also called race.

Tide rips. Small waves formed on the surface of wa-ter by the meeting of opposing tidal currents or bya tidal current crossing an irregular bottom. Verti-cal oscillation, rather than progressive waves, ischaracteristic of tide rips. See also: Rips.

Tide station. (1) The geographic location at whichtidal observations are made. (2) The equipment usedto make tidal observations and its housing.

Tide tables. Tables which give the predicted timesand heights of high and low water for every day inthe year for a number of reference stations, andtidal differences and ratios by which additional pre-dictions can be obtained for subordinate stations.From these values it is possible to interpolate by asimple procedure the height of the tide at any hourof the day. See also: Tidal Current Tables.

Toe (engineering). Terminal edge or edges of a struc-ture.

Tongue. A long, narrow strip of land, projecting intoa body of water; a long, narrow body of water in-denting the land or bounded by islands.


Topographic map. A map which presents the verti-cal position of features in measurable form as wellas their horizontal positions.

Topography. (1) The configuration of the surface ofthe earth, including its relief, the position of itsstream, roads, cities, etc. The earth�s natural andphysical features collectively. A single feature, suchas a mountain or valley, is termed a topographicfeature. Topography is subdivided into hypsogra-phy (the relief features), hydrography (the waterand drainage features), culture (artificial features),and vegetation. (2) The science of delineation of natu-ral and artificial features of a place or region espe-cially in a way to show their positions and eleva-tions.

Track. (1) The intended or desired horizontal direc-tion of travel with respect to the earth. The trackas expressed in degrees of the compass may be dif-ferent from the course due to such factors as mak-ing allowance for current sea or steering to resumethe track. (2) The path of intended travel with re-spect to the earth as drawn on the chart. Also calledintended track, trackline. (3) The actual path of avessel over the ground.

Traffic lane. An area within defined limits in whichone-way traffic is established. Natural obstacles,including those forming separation zones, may con-stitute a boundary.

Traffic separation scheme. A scheme which sepa-rates traffic proceeding in opposite or nearly oppo-site directions by the use of a separation zone orline, traffic lanes or by other means. Shipping cor-ridors marked by buoys, which separate incomingfrom outgoing vessels. Improperly called �sea lanes.�

Trench. A long, narrow, characteristically very deepand asymmetrical depression of the seafloor, withrelatively steep sides. See also: Trough.

Trough. (1) A long depression of the seafloor, charac-teristically flat bottomed and steep sided, and nor-mally shallower than a trench. (2) The lowest partof a wave, between two crests is called wave trough.

True north. The direction from any observer�s posi-tion to the geographical North Pole. The north di-rection of any geographic meridian.

Tule. Reed. Bulrush. A place where reeds grow. Cor-ruption of Spanish Tulares.

Tundra. One of the level or undulating treeless plainscharacteristic of arctic regions, having a black mucksoil with a permanently frozen subsoil.

Turning basin. A water area used for turning ves-sels.

Two-way route. A route within defined limits, in-side which two-way traffic is established, aimed atproviding safe passage of ships through waterswhere navigation is difficult or dangerous.

Under construction. The term used to indicate thatthe feature on the map is not completed but thatconstruction has started. It is distinguished from�proposed,� which means that the feature has beenplanned but construction has not been started.

Uniform state waterway marking system. A sys-tem developed jointly by the U.S. Coast Guard andstate boating administrators to assist the small-craftoperator in those state waters marked by partici-pating states. It consists of two categories of aids tonavigation. One is a system of aids to navigation,generally compatible with the federal lateral sys-tem of buoyage, to supplement the federal systemin state waters. The other is a system of regulatorymarkers to warn the small-craft operator of dan-gers or to provide general information and direc-tions.

United States Army Corps of Engineers (USACE).The Commanding General, United States ArmyCorps of Engineers (CGUSACE) serves as theArmy�s Real Property Manager, performing the full-cycle of real property activities (requirements, pro-gramming, acquisition, operation, maintenance,and disposal); manages and executes engineering,construction, and real estate programs for the Armyand the United States Air Force; and performs re-search and development in support of these pro-grams. CGUSACE manages and executes CivilWorks Programs. These programs include researchand development, planning, design, construction,operation and maintenance, and real estate activi-ties related to rivers, harbors and waterways; ad-ministration of laws for protection and preserva-tion of navigable waters and related resources suchas wetlands. CGUSACE assists in recovery fromnatural disasters.

United States Coast Guard (USCG). The U.S.Coast Guard, established by the Act of January 28,1915 (14 U.S.C. 1), became a component of the U.S.Department of Transportation on April 1, 1967,pursuant to the U.S. Department of Transporta-tion Act of October 15, 1966 (80 Stat. 931). The CoastGuard is a branch of the Armed Forces of the Un-tied States at all times and is a service within theU.S. Department of Transportation except when op-erating as part of the Navy in time of war or whenthe President of the United States directs.


U. S. Coast Pilot. A descriptive book for the use ofmariners, containing detailed information of coastalwaters, harbor facilities, etc., of an area. Such booksare prepared by NOAA for waters of the UnitedStates and its possessions.

Unsurveyed area. Areas on a map or chart whereboth relief and planimetric data are unavailable.These areas are usually labeled �unsurveyed.� Oran area on a map or chart which shows little or nocharted data because accurate information is lim-ited or not available.

Upland. A highland; ground elevated above the low-lands along a river or between hills.

Upper limit of navigability. The character of ariver will, at some point along its length, changefrom navigable to nonnavigable. Very often thatpoint will be at a major fall or rapids, or other placewhere there is a marked decrease in the navigablecapacity of the river. The upper limit will thereforeoften be the same point traditionally recognized asthe head of navigation, but may, under some of thetests described above, be at some point yet fartherupstream.

Upwelling. An upward flow of subsurface water dueto such cases as divergences, offshore winds, andwind drift transports away from shore.

Urban area. An area predominantly occupied by ar-tificial structures used for residential, commercial,and industrial purposes.

Valley. On the seafloor, a relatively shallow, widedepression, the bottom of which usually has a con-tinuous gradient. This term is generally not usedfor features that have canyonlike characteristics fora significant portion of their extent.

Variation. (1) The angle between the magnetic andgeographic meridians at any place, expressed indegrees and minutes east or west to indicate thedirection of magnetic north from true north. Theangle between magnetic and grid meridians is calledgrid magnetic angle, grid variation, or grivation.Called magnetic variation when a distinction isneeded to prevent possible ambiguity. Also calledmagnetic declination. (2) Change or difference froma given value.

Vertical lift bridge. A bridge with a movable spanbetween two lift towers such as the entire span canbe raised uniformly in the vertical direction.

Vessel. Includes every description of watercraft orother artificial contrivance used, or capable of be-

ing used, as a means of transportation on the wa-ters of the United States.

Vessel traffic service (VTS) area. Prescribe rulesfor vessel operation in order to prevent collisionsand groundings and to protect the navigable wa-ters of the VTS area from environmental harm fromcollisions and grounds.

Viaduct. A structure consisting of a series of archesor towers supporting a roadway, waterway, etc.,across a depression, etc. See also: Causeway.

Visibility. That property of the atmosphere whichdetermines the ability of an observer to see and iden-tify prominent objects by day, or lights or lightedobjects by night. A measure of this property is ex-pressed in units of distance. This term should notbe confused with visual range.

Visual range (of a light). The predicted range atwhich a light can be observed.

Volcano. An opening in the earth from which hotgases, smoke, and molten material issue, or a hillor mountain composed of volcanic material. A vol-cano is characteristically conical in shape with acrater in the top.

Warp. To move, as a vessel, from one place to anotherby means of lines fastened to an object, such as abuoy, wharf, etc., secured to the ground.

Warping buoy. A buoy so located that lines to it canbe used for the movement of ships.

Wash. The dry channel of an intermittent stream.

Watching properly. An aid on its assigned positionexhibiting the advertised characteristics in all re-spects.

Waterfront. Land at the end of a stream harbor, etc.The part of a city or town on such land; wharf ordock area.

Waterfront facility. All piers, wharves, docks, andsimilar structures to which a vessel may be secured;areas of land, water, or land and water under andin immediate proximity to them; buildings on suchstructures or contiguous to them and equipmentand materials on such structures or in such build-ings.

Water line. The line marking the junction of waterand land.

Watershed. The area drained by a stream.

Waterway. A water area providing a means of trans-


portation from one place to another, principally awater area providing a regular route for water traf-fic, such as a bay, channel, passage, or the regu-larly traveled parts of the open sea. The terms wa-terway, fairway, and thoroughfare have nearly thesame meanings.

Way point. A mark or place at which a vessel is re-quired to report to establish its position. (Also knownas �reporting point� or �calling-in-point.�)

Weir. A sort of fence set in a stream or along a shoreline to catch fish. It differs from a pound because itis mainly constructed of brush hedging or narrowboards with or without nettings. The terms weirand pound are, to a great extent, used interchange-ably in the United States. Also called brush weir,fish weir. Fish wiers are fixed solid structures madeof stones or stakes and wattlings, or a combinationof both. The simple form is a �Y� with the end to-ward high-water mark and the apex toward lowwater. In the apex there is very often a special cageor trap for the concentration or retention of thecatch. Coastal weirs are generally built where thereis a large expanse of ground left uncovered at lowwater. Weirs are usually kept in position all yearround.

Weir jetty. An updrift jetty with a low section or weirover which littoral drift moves into a predredgeddeposition basin which is dredged periodically.

Wellhead. A submarine structure projecting somedistance above the seabed and capping a temporarilyabandoned or suspended oil or gas well. See also:Submerged production well.

Wetlands. Those areas that are inundated or satu-rated by surface or ground water at a frequencyand duration sufficient to support, and that undernormal circumstances do support, a prevalence ofvegetation typically adapted for life in saturated soilconditions. Wetlands generally include swamps,marshes, bogs, and similar areas.

Wharf. A structure of open, rather than solid con-struction, along a shore or bank which providesberthing for ships and which generally providescargo-handling facilities. A similar facility of solidconstruction is called quay.

Winter light. A light which is maintained duringthose winter months when the regular light is ex-tinguished. It is of lower candlepower than the regu-lar light but usually of the same characteristic.

Winter marker. A lighted or unlighted buoy without

sound signal, which is established as a replacementduring the winter months when other aids are closedor withdrawn.

Wire drag. An apparatus for surveying rock areaswhere the normal sounding methods are insufficientto insure the discovery of all existing obstructions,pinnacles, rocks, etc., above a given depth or fordetermining the least depth of an area. It consistsessentially of a buoyed wire towed at the desireddepth by two launches. Often shortened to drag.

Withdrawn. The discontinuing of a floating aid dur-ing severe ice conditions or for the winter season.

World Geodetic System 1972 (WGS 72) A systemcomprised of a consistent set of parameters describ-ing the size and shape of the earth, the positions ofa network of points with respect to the center ofmass of the earth, transformations from major geo-detic datums, and the potential of the earth (usu-ally in terms of harmonic coefficients). WGS 72 rep-resents the Defense Mapping Agency�s (DMA�s) mod-eling of the earth from a geometric, geodetic, andgravitational standpoint using data available in1972.

World Geodetic System 1984 (WGS 84). A systemcomprised of a consistent set of parameters describ-ing the size and shape of the earth, the positions ofa network of points with respect to the center ofmass of the earth, transformations from major geo-detic datums, and the potential of the earth (usu-ally in terms of harmonic coefficients). WGS 84 rep-resents the U.S. Defense Mapping Agency�s (DMA�s)modeling of the earth from a geometric, geodetic,and gravitational standpoint using data, techniques,and technology available in 1984.

Wreck. The ruined remains of a vessel which has beenrendered useless, usually by violent action, as bythe action of the sea and weather on a stranded orsunken vessel. In hydrography the term is limitedto a wrecked vessel, either submerged or visible,which is attached to or foul of the bottom or cast upon the shore.

Wreck buoy. A buoy marking the position of a wreck.It is usually placed on the seaward or channel sideof the wreck and as near to the wreck as conditionswill permit. To avoid confusion in some situations,two buoys may be used to mark the wreck. Thepossibility of the wreck having shifted position dueto sea action between the times the buoy was estab-lished and later checked or serviced should not beoverlooked.


Wrecks. Charted wrecks are of two kinds: strandedwreck, where any portion of the hull is above thechart datum; and sunken wreck, where the hull isbelow the chart datum or where the masts only arevisible.

X-axis. A horizontal axis in a system of rectangularcoordinates; that line on which distances to the rightor left (east or west) of the reference line are marked,especially on a map, chart, or graph.

Yard. A fundamental unit of length in the Englishsystem of measurement. The metric equivalent priorto July 1, 1959, was 1 year = 0.91440183 meter. Onthat date the value was changed to 1 yard = 0.9144meter. This change will not apply to any data ex-pressed in feet derived from and published as a re-sult of geodetic surveys within the United Statesuntil such time as the basic geodetic survey net-works are readjusted. See: Mile, nautical.

Y-Axis. A vertical axis in a system of rectangular co-ordinates; that line on which distances above orbelow (north or south of) a reference line aremarked, especially on a map, chart, or graph. Theline which is perpendicular to the X-axis and passesthrough the origin.

NOAA'S NATIONAL OCEAN SERVICECATALOGS OF CHART PRODUCTS



NOS—PRODUCTS___Aeronautical Catalog�(U.S.)___Nautical Catalog 1�(Atlantic and Gulf Coast)___Nautical Catalog 2�(Pacific Coast)___Nautical Catalog 3�(Alaska)___Nautical Catalog 4�(Great Lakes)

___Dates of Latest Editions: Nautical

Name: _________________________

Address: _______________________

_____________________________

_____________________________

_____________________________

NIMA—PRODUCTS___Aeronautical Catalog�(World)

NIMA Nautical:___Region 1�(U.S., Canada)___Region 2�(Central, South America, Antarctica)___Region 3�(W. Europe, Arctic, Greenland, Iceland)___Region 4�(Scandinavia, Baltic, Soviet Union)___Region 5�(W. Africa, Mediterranean)___Region 6�(Indian Ocean)___Region 7�(Australia, Indonesia, N. Zealand)___Region 8�(Oceania)___Region 9�(East Asia)







Name: _________________________

Address: _______________________

_____________________________

_____________________________

_____________________________

Name: _________________________

Address: _______________________

_____________________________

_____________________________

_____________________________






______________________________________________________________________________

DISTRIBUTION BRANCH, N/ACC33NATIONAL OCEAN SERVICERIVERDALE, MD 20737-1199

______________________________________________________________________________


______________________________________________________________________________


APPENDIX B

PART I. INDEX OF ABBREVIATIONS(Section V of Chart No. 1)

Abbreviation ........ Meaning ...........................Symbol(if applicable)

___________________________________________________

AAERO, Aero .. Aero light ..................................... P 60

AERO RBn ... Aeronautical radiobeacon............ S 16

Aero RC........ Aeronautical radiobeacon............ S 16

Al .................. Alternating .............................. P 10.11

ALP .............. Articulated Loading Platform ....... L 12

Alt ................. Alternating .............................. P 10.11

Am ................Amber ...................................... P 11.8

anc ............... Ancient ........................................ O 84

ANCH, Anch .Anchorage ........................ N 20, O 21

approx .......... Approximate ................................ O 90

Apprs ............ Approaches ................................. O 22

BB ................... Bay, bayou ....................................O 4

Bdy Mon ....... Boundary monument ................... B 24

bk ................. Broken .........................................J 33

Bkw .............. Breakwater ................................. F 4.1

B l .................. Blue.......................................... P 11.4

BM ................Bench mark ................................. B 23

Bn ................. Beacon .......................................... O 4

Bn Tr ............. Beacon tower ................................ O 3

B r.................. Breakers ..................................... K 17

brg ................Bearing ....................................... B 62

brk ................Broken .........................................J 33

Bu ................. Blue.......................................... P 11.4

Cc ................... Course .........................................J 32

C................... Can, cylindrical ............................ Q 21

C................... Cove ............................................. O 9

CALM ...........Centenary Anchor Leg Mooring... L 16

Cas ............... Castle ....................................... E 34.2

Cb ................. Cobbles ..........................................J 8

Cbl ................Cable .......................................... B 46

Cd ................. Candela ...................................... B 54

CD ................Chart datum .................................. H 1

Cem .............. Cemetery .................................... E 19

CG ................Coast Guard station .................... T 10

Chan .............Channel ...................................... O 14

Ch. ................Church ...................................... E10.1

Chy ............... Chimney ...................................... E 22

Cl ..................Clay................................................J 3

CL ................. Clearance ......................... D 20, D 21

cm ................Centimeter(s) .............................. B 43

Co ................. Coral ............................................ J 10

Co rf .............Coral reef ....................................O 26

Cr ................. Creek ............................................ O 7


___________________________________________________

Appendix B–Abbreviations B–1

NOAA Chart User's ManualB�2

PART I. INDEX OF ABBREVIATIONS (Section V of Chart No. 1)_____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

crs ................Course .........................................J 32

Cup, Cup. ..... Cupola ..................................... E 10.4

Cus Ho ......... Customs House .......................... F 61

Cy ................. Clay................................................J 3

DD................... Destroyed ................................... O 94

Destr ............. Destroyed ................................... O 94

dev ............... Deviation ..................................... B 67

DIA, Dia ........ Diaphone..................................... R 11

Dir ................. Direction ............................. P 30, P 31

dist ................Distant......................................... O 85

dm ................Decimeter(s) ............................... B 42

Dn. ................Dolphin ........................................ F 20

Dol. ............... Dolphin ........................................ F 20

DW ............... Deep Water route ........ M 27.1, N 12.4

DZ ................Danger Zone ............................... Q 50

EE ................... East, eastern ............................... B 10

ED ................Existence doubtful .......................... I 1

E E Z .............. Exclusive Economic Zone ........... N 47

E Int .............. Equal interval, isophase ........... P 10.3

Entr ............... Entrance ..................................... O 16

Est ................Estuary........................................ O 17

exper ............ Experimental ............................... O 93

Explos .......... Explosive .................................... R 10

Exting, exting Extinguished ............................... P 55

Ff .................... Fine ..............................................J 30

F ................... Fixed ........................................ P 10.1

Fd ................. Fjord ..............................................O 5

F Fl ............... Fixed and flashing .................. P 10.10

F ISH ............. Fishing ........................................ N 21

F l .................. Flashing ................................... P 10.4

Fla ................Flare stack ................................... L 11

fm ................. Fathom ........................................ B 48

fms ............... Fathoms ...................................... B 48

fne ................Fine ..............................................J 30

Fog Det Lt..... Fog detector light ........................ P 62

Fog Sig ......... Fog signal ..................................... R 1

F P ................. Flagpole ...................................... E 27

FS, FS. ......... Flagstaff ...................................... E 27

ft ................... Foot, feet ..................................... B 47

GG .................. Gravel ............................................ J 6

G .................. Green ....................................... P 11.3

G .................. Gulf ............................................... O 3

Gp Fl ............ Group flashing .......................... P 10.4

GP Occ ......... Group occulting ........................ P 10.2

Hh ................... Hard .............................................J 39

h ................... Hour ............................................ B 49

H ................... Pilot transferred by helicopter..... T 1.4

HAT .............. Highest astronomical tide .............. H 3

Hbr Mr .......... Harbormaster .............................. F 60

Historic Wk ... Historic wreck ............................. N 26

Hk ................. Hulk............................................. F 34

Hor ............... Horizontally disposed .................. P 15

Hor Cl ...........Horizontal clearance ................... D 21

Hosp ............. Hospital .................................... F 62.2

hr .................. Hour ............................................ B 49

hrd ................Hard .............................................J 39

IIALA ............. International Association of

.....................Lighthouse Authorities ............... Q 130

in .................. Inlet ..............................................O10

Intens ........... Intensified.................................... P 45

Int Qk Fl ........ Interrupted quick flashing ......... P 10.6

IQ ................. Interrupted quick flashing ......... P 10.6

Appendix B�Abbreviations. B�3

PART I. INDEX OF ABBREVIATIONS (Section V of Chart No. 1)____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

I Qk Fl ........... Interrupted quick flashing ......... P 10.6

Iso ................ Isophase .................................. P 10.3

IUQ ............... Interrupted ultra quick .............. P 10.8

Kkm ................Kilometer(s)................................. B 40

kn ................. Knot(s) ........................................ B 52

LL ................... Loch, lough, lake ........................... O 6

Lag ............... Lagoon .......................................... O 8

LANBY.......... Large Automatic Navigational Buoy ... P 8

Lat, lat ...........Latitude ......................................... B 1

LASH ............ Lighter aboard ship ................... G 184

LAT ............... Lowest astronomical tide ............... H 2

Ldg ............... Landing ....................................... F 17

Ldg ............... Leading ....................................... P 21

Le ................. Ledge .......................................... O 28

L Fl ............... Long flashing............................ P 10.5

Lndg ............. Landing ....................................... F 17

LNG .............. Liquified natural gas .................. G 185

Long, long ..... Longitude ...................................... B 2

LOP .............. Line of position .......... S 21, S 31, S 41

LPG .............. Liquified petroleum gas ............. G 186

L S S .............. Life saving station ....................... T 12

Lt .................. Light .............................................. P 1

Lt Ho ............. Lighthouse .................................... P 1

Lt V ............... Light vessel ................................... O 6

Mm .................. Meter(s) ...................................... B 41

m .................. Minute(s) of time ......................... B 50

m .................. Medium (in relation to sand) ......... J 31

M .................. Mud, muddy ...................................J 2

M .................. Nautical mile(s) ........................... B 45

mag .............. Magnetic ..................................... B 61

MHHW .......... Mean higher high water ............... H 13

MHLW ...........Mean higher low water ................ H 14

MHW ............ Mean high water ........................... H 5

MHWN .......... Mean high water neaps ............... H 11

MHWS .......... Mean high water springs ............... H 9

Mi ................. Nautical mile(s) ........................... B 45

mn ................Minute of time ............................. B 50

Mk ................Mark .......................................... Q 101

MLHW .......... Mean lower high water ................ H 15

MLLW ...........Mean lower low water ................. H 12

MLW .............Mean low water ............................. H 4

MLWN...........Mean low water neaps ................ H 10

MLWS ...........Mean low water springs ................ H 8

mm ............... Millimeter(s) ................................ B 44

Mo ................Morse ....................................... P 10.9

MON, Mon,

Mon. .......... Monument .......................... B 24, E 24

MSL .............. Mean sea level .............................. H 6

Mt ................. Mountain ..................................... O 32

Mth ............... Mouth .......................................... O 19

NN................... North, northern .............................. B 9

N................... Nun ............................................. Q 20

NE ................Northeast .................................... B 13

NM ................Nautical mile(s) ........................... B 45

N Mi .............. Nautical mile(s) ........................... B 45

No ................. Number .................................... N 12.2

NP ................Neap tide..................................... H 17

NW ............... Northwest .................................... B 15

NWS SIG

STA ...........Weather signal station ................. T 29

OObsc .............Obscured .................................... P 43

Obscd ...........Obscured .................................... P 43

Obs spot ....... Observation spot ......................... B 21

Obstn ............ Obstruction ............... K 40, K 41, K 42

NOAA Chart User's ManualB�4

PART I. INDEX OF ABBREVIATIONS (Section V of Chart No. 1)_____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

Obstr ............ Obstruction ................................. K 41

Oc................. Occulting .................................. P 10.2

Occ ............... Occulting .................................. P 10.2

Occas ...........Occasional .................................. P 50

ODAS ...........Ocean Data Acquisition System .. Q 58

Or ................. Orange ..................................... P 11.7

PP ................... Pebbles ..........................................J 7

P ................... Pillar ............................................ Q 23

PA ................. Position approximate ..................... B 7

Pass ............. Passage, pass ............................ O 13

PD ................Position doubtful ............................ B 8

PTL STA ....... Pilot station ................................... T 3

Pk ................. Peak ............................................ O 35

Post Off ........ Post office ................................... F 63

Priv, priv........ Private............................... P 65, Q 70

Prod. well ......Production well ............................ L 20

PROHIB........ Prohibited ................ N 2.2, N 20, N 21

Pyl ................Pylon ........................................... D 26

QQ .................. Quick........................................ P 10.6

Qk Fl ............. Quick flashing .......................... P 10.6

RR ................... Coast radio station

.....................providing QTG services .............. S 15

R ................... Red .......................................... P 11.2

R ................... Rocky .............................................J 9

Ra ................. Radar reference line................... M 32

Ra (conspic) .Radar conspicuous object ............. S 5

Ra Antenna ... Dish aerial ................................... E 31

Racon ...........Radar transponder beacon ........... S 3

Radar Sc. ..... Radar scanner ......................... E 30.3

Radar Tr. ....... Radar tower ............................. E 30.2

Radome, Ra

Dome ........ Radar dome ............................. E 30.4

Ra Ref .......... Radar reflector .............................. S 4

RBn .............. Circular radiobeacon ................... S 10

RC ................Circular radiobeacon ................... S 10

Rd ................. Roads, roadstead ........................ O 22

RD ................Directional radiobeacon .............. S 11

RDF .............. Radio direction finding station ..... S 14

Ref. ............... Refuge ...................................... Q 124

Rep ............... Reported ........................................ I 3

Rf.................. Reef ............................................ O 26

RG ................Radio direction finding station ..... S 14

R k ................. Rocky .............................................J 9

Rky ............... Rocky .............................................J 9

R Mast .......... Radio mast .................................. E 28

Ro Ro ...........Roll on Roll off ............................. F 50

R Sta ............ Coast radio station

.....................providing QTG services .............. S 15

R Tower ........ Radio tower ................................. E 29

Ru ................. Ruins................................. D 8, F 33.1

RW ............... Rotating radiobeacon .................. S 12

SS ................... Sand ..............................................J 1

S ................... South, southern ........................... B 11

S ................... Spar, spindle ............................... Q 24

s ................... Second of time ............................ B 51

SALM ...........Single Anchor leg Mooring .......... L 12

SBM ............. Single Buoy Mooring ................... L 16

Sc ................. Scanner ................................... E 30.3

Sd ................. Sound ......................................... O 12

S D ................Sounding doubtful .......................... I 2

S E ................Southeast .................................... B 14

sec ................Second of time ............................ B 51

sf .................. Stiff ............................................... J 36

sft ................. Soft ..............................................J 35

S H ................Shells ...........................................J 12

Shl ................Shoal........................................... O 25

S i .................. Silt ..................................................J 4

so ................. Soft ..............................................J 35

Appendix B�Abbreviations. B�5

PART I. INDEX OF ABBREVIATIONS (Section V of Chart No. 1)____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

Sp ................. Spring tide ................................... H 16

S P ................Spherical ..................................... Q 22

Sp. ................Spire ........................................ E 10.3

Spipe ............ Standpipe .................................... E 21

SPM ............. Single point mooring ................... L 12

S S ................Signal station .............................. T 20

st .................. Stones............................................ J 5

stf ................. Stiff ............................................... J 36

stk................. Sticky ...........................................J 34

Str ................. Strait ........................................... O 11

Subm ............ Submerged ................................. O 93

Subm piles .... Submerged piles ...................... K 43.1

Subm ruins ... Submerged ruins ...................... F 33.2

sy.................. Sticky ...........................................J 34

S W ............... Southwest ................................... B 16

TT ................... True ............................................ B 63

t .................... Metric ton(s) ................................ B 53

Tel ................. Telephone, telegraph ................... D 27

Temp, temp ... Temporary ................................... P 54

T k ................. Tank ............................................ E 32

Tr, Tr., TR ......Tower .............................. E 10.2, E 20

T T ................. Tree tops ..................................... C 14

TV Mast ........ Television mast ........................... E 28

TV Tower ......Television tower .......................... E 29

UUncov ...........Uncovers ..................................... K 11UQ ................Ultra quick ................................ P 10.8

Vv ................... Volcanic ....................................... J 37var ................Variation ...................................... B 60Vert ............... Vertically disposed ...................... P 15Vert Cl ...........Vertical clearance ........................ D 20Vi ..................Violet ........................................ P 11.5Vil ................. Village ........................................... D 4VLCC ............ Very large crude carrier ............. G 187vol ................. Volcanic ....................................... J 37VQ ................Very quick ................................ P 10.7V Qk Fl ......... Very quick flash ........................ P 10.7

WW ..................West, western ............................. B 12W ..................White........................................ P 11.1Wd ................Weed ........................................ J 13.1WGS .............World Geodetic System .............. S 50Whf ............... Wharf .......................................... F 13WHIS, Whis .. Whistle ........................................ R 15Wk ................Wreck ............ K 20–23, K 26–27, K 30

YY ................... Yellow ....................................... P 11.6

NOAA Chart User's ManualB–6

PART II. INDEX OF ABBREVIATIONS—Supplementary National Abbreviations(Section V of Chart No. 1)

AApt ................Apartment ...................................... E s

BB ................... Black ..............................................Qq

bk ................. Black ............................................. Jas

bl .................. Black ............................................. Jas

Blds .............. Boulders .......................................... Je

br .................. Brown ............................................ Jaz

Bu ................. Blue............................................... Jau

CCap ............... Capitol ............................................. Et

Ch ................. Chocolate ...................................... Jba

Chec ............. Checkered .....................................Qo

ck.................. Chalk................................................Jf

Cn ................. Cinders ...........................................Jp

Co ................. Company ....................................... Eu

Co Hd ...........Coral head ....................................... Ji

COLREGS .... Collision regulations ....................... Na

Corp ............. Corporation .................................... Ev

cps ................Cycles per second .......................... B j

CRD ............. Columbia River Datum .................... Hj

c/s................. Cycles per second .......................... B j

Ct Ho ............ Court house ................................... Eo

Ddec ............... Decayed........................................ Jan

deg ............... Degree(s) ....................................... Bn

Di .................. Diatoms .........................................Jaa

Diag .............. Diagonal bands ..............................Qp

Discol water .. Discolored water ............................ Ke

dk ................. Dark ..............................................Jbd

EExplos Anch .. Explosives anchorage .................... Qk

FFacty ............ Factory ........................................... Ed

F Gp Fl ......... Fixed and group flashing ................ Pd

fl ................... Flood .............................................. Hq

fly.................. Flinty ............................................. Jao

F r .................. Foraminifera .................................... Jy

Fu ................. Fucus .............................................Jaf

GGAB, Gab ..... Gable .............................................. E i

GCLWD ........ Gulf Coast Low Water Datum ......... Hk

Gl.................. Globigerina ...................................... Jz

glac ............... Glacial ........................................... Jap

gn ................. Green ............................................ Jav

Govt Ho ........ Government house ....................... Em

Grd ............... Ground ............................................ Ja

Grs ............... Grass .............................................. Jv

gty ................Gritty ............................................ Jam

GUN ............. Fog gun .......................................... Rd

gy ................. Gray ..............................................Jbb

HHECP ...........Harbor entrance control point ......... Tb


___________________________________________________


___________________________________________________

Appendix B—Abbreviations. B–7


____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

HHW............. Higher high water ........................... Hb

H S ................High school .................................... Eg

ht .................. Height ............................................ Hp

HW ............... High water ...................................... Hq

HWF & C ......High water full and change ............. Hh

H z ................. Hertz .............................................. Bg

Iin .................. Inch ................................................ Bc

ins ................. inches ............................................ Bc

Inst ............... Institute .......................................... En

ISLW ............. Indian springs low water ................. Hg

KK ................... Kelp................................................. Ju

kc.................. Kilocycle ......................................... Bk

kHz ............... Kilohertz ......................................... Bh

kn ................. Knot(s) ........................................... Ho

LLa ................. Lava ................................................. Jl

LLW .............. Lower low water ............................. He

LOOK TR ......Lookout tower ................................. T f

lrg ................. Large.............................................. Jai

lt ................... Light .............................................. Jbc

Ltd ................Limited ............................................ E r

LW ................Low water ...................................... Hc

LWD .............. Low water datum ............................ Hd

LWF & C ....... Low water full and change............... Hi

Mm2

.............................. Square meter(s) ............................. Ba

m3.............................. Cubic meter(s) ............................... Bb

Ma ................Mattes ........................................... Jag

Magz ............ Magazine ........................................ E l

Mc ................Megacycle(s) .................................. B l

Mds .............. Madrepores ...................................... Jj

MHz .............. Megahertz ....................................... B i

Ml ................. Marl ................................................. Jc

Mn ................Manganese ..................................... Jq

Mo ................Morse code ..................................... Rf

Ms ................Mussels ........................................... J s

MTL .............. Mean Tide Level .............................. Hf

NNAUTO ......... Nautophone ................................... Rc

Oor ..................Orange .......................................... Jax

Oys ............... Oysters ........................................... Jr

Oz................. Ooze ............................................... Jb

PPav ............... Pavillion.......................................... Ep

Pm ................Pumice ...........................................Jm

Po ................. Polyzoa .........................................Jad

Pt ..................Pteropods ..................................... Jac

QQuar .............Quarantine ..................................... Fd

Qz................. Quartz .............................................Jg

RRd ................. Radiolaria ......................................Jab

rd ..................Red ............................................... Jay

rt ................... Rotten ............................................ Jaj

Ry ................. Railway, railroad ............................. Db

SSc ................. Scoriae ............................................ Jo

Sch ............... Schist ..............................................Jh

Sch ............... School ............................................. Ef

Sem .............. Semaphore .................................... Tg

Sh ................. Shingle ............................................ Jd


S-LFl ............. Short-long flashing ......................... Pb

sml ................Small ............................................. Jah

Spg ............... Sponge ............................................Jt

Spi ................Spicules .......................................... Jx

spk ................Speckled ........................................ Jal

Stg ................Seatangle ....................................... Jw

St M .............. Statute mile(s) ................................ Be

St Mi ............. Statute mile(s) ................................ Be

Str ................. Stream ............................................ Hl

str ................. Streaky.......................................... Jak

SUB-BELL .... Submarine fog bell ......................... Ra

Subm crib ..... Submerged crib ............................... K i

SUB-OSC ..... Submarine oscillator....................... Rb

Sub vol ......... Submarine volcano ........................ Kd

TT ................... Telephone ................................. Eq,Qt

T ................... Short ton(s) ................................... Bm

T ................... Tufa ................................................. Jn

Tel ................. Telegraph ....................................... Qs

Tel off ............ Telegraph office .............................. Ek

ten ................Tenacious...................................... Jaq

Uunev ............. Uneven ..........................................JbfUniv .............. University ....................................... Ehus ................. Microsecond(s) ............................... Bfusec .............. Microsecond(s) ............................... Bf

Vvard .............. Varied ............................................ Jbevel ................. Velocity .......................................... Hnvi ................... Violet ..............................................JatVol Ash ......... Volcanic ash .................................... Jk

Wwh ................. White............................................. JarWHIS ............ Whistle ........................................... Qc

Yyd ................. Yard ............................................... Bdyds ................Yards .............................................. Bdyl ................... Yellow ........................................... Jaw


____________________________________________________________________________________________________

Abbreviation ......... Meaning ........................... Symbol(if applicable)

___________________________________________________

Abbreviation ......... Meaning ........................... Symbol(if applicable)

___________________________________________________

PART III. INTERNATIONAL ABBREVIATIONS(Section W of Chart No. 1)


B Positions, Distances, Direc-tions, Compass

PA ................. Position approximate ..................... B 7

PD ................Position doubtful ............................ B 8

N................... North ............................................. B 9

E ................... East............................................. B 10

S ................... South .......................................... B 11

W .................. West ............................................ B 12

NE ................Northeast .................................... B 13

S E ................Southeast .................................... B 14

NW ............... Northwest.................................... B 15

S W ............... Southwest ................................... B 16

km ................Kilometer(s)................................. B 40

m .................. Meter(s) ...................................... B 41

dm ................Decimeter(s) ............................... B 42

cm ................Centimeter(s) .............................. B 43

mm ............... Millimeter(s) ................................ B 44

M .................. Nautical mile(s), Sea mile(s) ....... B 45

ft ................... Foot/feet ...................................... B 47

h ................... Hour ............................................ B 49

m, min...........Minute(s) of time ......................... B 50

s, sec ............ Second(s) of time ........................ B 51

kn ................. Knot(s) ........................................ B 52

t .................... Ton(s) .......................................... B 53

cd ................. Candela (new candela) ............... B 54

D Cultural FeaturesRu ................. Ruin .............................................. D 8

F PortsLndg ............. Landing for boats ........................ F 17

RoRo ............ Roll-on, Roll-off Ferry .................. F 50

I DepthsED ................Existence doubtful ........................... l 1

S D ................Sounding doubtful ........................... l 2

K Rocks, Wrecks, ObstructionsBr ..................Breakers ..................................... K 17

WK ............... Wreck .......................................... K 20

Obstn ............ Obstruction ................................. K 40

L Offshore Installations,Submarine Cables, SubmarinePipelines

Fla ................Flare stack ................................... L 11

Pro ................Submerged Production ............... L 20

Well .............. Well

M Tracks, RoutesRa ................. Radar ......................................... M 31

DW ............... Deep Water ..............................M 27.2

N Areas, LimitsNo ................. Number .................................... N 12.2

DW ............... Deep Water .............................. N 12.4

O Hydrographic TermsSMt ............... Seamount ....................................O 33

P LightsLt ..................Light .............................................. P 1


___________________________________________________


___________________________________________________


PART III. INTERNATIONAL ABBREVIATIONS (Section W of Chart 1)

_____________________________________________________________________________________________________


___________________________________________________


___________________________________________________

F ................... Fixed ........................................ P 10.1

Oc................. Occulting .................................. P 10.2

Iso ................ Isophase .................................. P 10.3

F l .................. Flashing ................................... P 10.4

LF l ................Long-flashing ........................... P 10.5

Q .................. Quick........................................ P 10.6

IQ ................. Interrupted quick ...................... P 10.6

VQ ................Very quick ................................ P 10.7

IVQ ............... Interrupted very quick .............. P 10.7

UQ ................Ultra quick ................................ P 10.8

IUQ ............... Interrupted ultra quick .............. P 10.8

Mo ................Morse Code ............................. P 10.9

W .................. white ........................................ P 11.1

R ................... red............................................ P 11.2

G .................. green........................................ P 11.3

Bu ................. blue .......................................... P 11.4

Vi .................. violet ........................................ P 11.5

Y ................... yellow/orange/Amber ............... P 11.6

Or ................. Orange ..................................... P 11.7

Am ................Amber ...................................... P 11.8

Ldg ............... Leading light ............................. P 20.3

Dir ................. Direction light .............................. P 30

occas ............ occasional ................................... P 50

R lts .............. Air obstruction lights ................. P 61.2

priv ............... private ......................................... P 65

Fog Det Lt..... Fog detector light ........................ P 62

Aero .............. Aeronautical ........................ P 60/61.1

Q Buoys, BeaconsDZ ................Danger Zone ............................... Q 50

ODAS ...........Ocean Data Acquisition System .. Q 58

Mk ................mark .......................................... Q 101

IALA ............. International Association of Lighthouse

Authorities ................................. Q 130

R Fog SignalsExplos .......... Explosive .................................... R 10

Dia ................Diaphone..................................... R 11

Whis ............. Whistle ........................................ R 15

S Radar, Radio, ElectronicPosition-Fixing Systems

Ra ................. Coast Radar Station ...................... S 1

Racon ...........Radar transponder beacon ........... S 3

F Racon ........ Radar transponder beacon,

responding on a fixed frequency

outside the marine band ............. S 3.4

RC ................Circular (non-directional) marine

radiobeacon ................................ S 10

RD ................Directional radiobeacon .............. S 11

RW ............... Rotating-pattern radiobeacon ...... S 12

RG ................Radio direction-finding stations ... S 14

R ................... QTG service, Coast

..................... radio stations............................... S 15

Aero RC........ Aeronautical radiobeacon............ S 16

WGS............. World Geodetic System .............. S 50

T ServicesS S ................Signal station .............................. T 20

INT ............... international ................................ T 21


AABAND .................. Abandoned

A/C ........................ Aircraft

AERO RBN ............ Aeronautical radiobeacon

ANCH .................... Anchorage

ANCH PROHIB ...... Anchorage prohibited

ANMS .................... Automated Notice to Mariners

APPROX ................ Approximate

ART DBN ............... Articulated daybeacon

ART LT ................... Articulated light

ATLC ...................... Atlantic

ATON ..................... Aids to Navigation

AUTH ..................... Authorized

AUTH CL ................ Authorized Clearance

AVG ....................... Average

BBKW ...................... Breakwater

BLDG ..................... Building

BNM ...................... Broadcast Notice to Mariners

BRG ....................... Bearing

CC............................ Can

(C).......................... Indicates chart has Loran-C TDs

overprinted

CFR ....................... Code of Federal Regulations

CGUSACE ............. Commanding General, U.S. Army

Corps of Engineers

CHAN .................... Channel

COE ....................... Corps of Engineers

COLREGS ............. Collision Regulations

COMDTINST .......... Commandant Instruction

COMDTPUB........... Commandant Publication

CONT ..................... Continue

COTP ..................... Captain of the Port

CUP ....................... Cupola

DD............................ Indicates NAD 1983 added

DEG ....................... Degrees (Temperature; geo pos)

DESTR................... Destroyed

DGPS .................... Differential Global Positioning

System

DIA......................... Diameter

DISCONTD ............. Discontinued

DMA ...................... Defense Mapping Agency

DOD ....................... Department of Defense

DR ......................... Dead Reckoning

DW ........................ Deep Water Route

EE ............................ New Edition

ECDIS .................... Electronic Chart Display and

Information Systems

ED ......................... Edition

ED ......................... Existence Doubtful

E E Z ....................... Exclusive Economic Zone

E F F ....................... Effect/Effective

E L B ....................... Exposed Location Buoy

ENTR ..................... Entrance

EPA ....................... United States Environmental

Protection Agency

ESTAB ................... Established

EXPLOS ANCH ...... Explosive Anchorage

Abbreviation ........ Meaning

___________________________________________________

PART IV. ABBREVIATIONS USED THIS MANUAL, NM,LNM, LIGHT LIST, BROADCAST NOTICE TOMARINERS, NAUTICAL CHART CATALOG, ORDATES OF LATEST EDITIONS


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PART IV. ABBREVIATIONS USED THIS MANUAL, NM, LNM, LIGHT LIST, BROADCAST NOTICE TOMARINERS, NAUTICAL CHART CATALOG, OR DATES OF LATEST EDITIONS

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NOAA Chart User's Manual

FFAD ....................... Fish Aggregating Device

FCC ....................... Federal Communications

Commission

FCZ ........................ Fishery Conservation Zone

FM(S) .................... Fathom(s)

FOG SIG ................ Fog Signal Station

F P.......................... Flag Pole

F R.......................... Federal Register

F S.......................... Flag Staff

F T .......................... Foot/Feet

F TR ....................... Flag tower

F/V......................... Fishing Vessel

GG ........................... Green

GPS ....................... Global Positioning System

GRI ........................ Group Repetition Interval

HHBR ....................... Harbor

HO ......................... House

HOR CL ................. Horizontal Clearance

HR ......................... Hour

HT .......................... Height

HZ .......................... Hertz

IIALA ....................... International Association of

Lighthouse Authorities

ICW ....................... Intracoastal Waterway

IGLD ...................... International Great Lakes Datum

IHB......................... International Hydrographic Bureau

IHO ........................ International Hydrographic

Organization

IMCO ..................... Inter-governmental Maritime

Consultantive Organization

IMO ........................ International Maritime

Organization

ITU ......................... International Telecommunications

Union

KKHZ ....................... Kilohertz

KM ......................... Kilometer

KT(S) ..................... Knot(s)

LLANBY................... Large Automated Navigation

Buoy

LAT ........................ Latitude

L B .......................... Lighted Buoy

L B B ....................... Lighted Bell Buoy

LGB ....................... Lighted Gong Buoy

LHB ....................... Lighted Horn Buoy

LLNR...................... Light List Number

LLWD ..................... Lower Low Water Datum

LNB ....................... Large Navigation Buoy

LNG ....................... Liquidifed Natural Gas

LNM ....................... Local Notice to Mariners

LONG .................... Longitude

Look TR ................. Lookout Tower

LOOP .................... Louisiana Offshore Oil Port

LOP ....................... Line of Position

Loran...................... Long-Range Navigation

LT ........................... Light

LT HO .................... Light House

LT OBSC ................ Light Obscured

LWB ....................... Lighted Whistle Buoy

LWD ....................... Low Water Datum

Appendix B—Abbreviations. B–13


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MM ........................... Metric Chart

MAINTD ................. Maintained

MAX ....................... Maximum

MB ......................... Millibar

MDT ....................... Moderate

MF ......................... Marine Facility Chart

MHHW ................... Mean Higher High Water

MHW ..................... Mean High Water

MHWL ................... Mean High Water Line

MHZ ....................... Megahertz

MICRO TR.............. Microwave Tower

MIN ........................ Minute (time; geo pos)

MLLW .................... Mean Lower Low Water

MLW ...................... Mean Low Water

MLWL .................... Mean Low Water line

MM ........................ Millimeter

Mo (A) .................... Morse Alpha

MSL ....................... Mean Sea Level

MT ......................... Mountain, Mount

M/V ........................ Motor Vessel

MWLL .................... Mean Water Level Line

NN............................ New Chart

N............................ Nun

NAD ....................... North American Datum

NAE ....................... National Academy of Engineering

NAS ....................... National Academy of Sciences

NIMA...................... National Imagery and Mapping

Agency

NM ......................... Nautical Mile(s)

NM ......................... Notice to Mariners

NOAA .................... National Oceanographic &

Atmospheric Administration

NOS ....................... National Ocean Service

NRC ....................... National Research Council

NWS ...................... National Weather Service

OO ........................... Omega Chart

OBSTR .................. Obstruction

OCCASION ............ Occasion/Occasionally

OCS ....................... Outer continental shelf

ODAS .................... Oceanographic (or Ocean) Data

Acquisition System

OPAREA ................ Operating Area

OVHD PWR CAB... Overhead Power Cable

PPA.......................... Position Approximate

PAC ....................... Pacific

P/C ........................ Pleasure Craft

PD ......................... Position Doubtful

PPC ....................... Pumping Platform Complex

PPI......................... Plan Position Indicator

P R E S .................... Pressure

PRIV ...................... Private, Privately

PRIV MAINTD ........ Privately Maintained

PROHIB ................. Prohibited

PSN ....................... Position

PT(S) ..................... Point(s)

PUB ....................... Publication

PWI ....................... Potable Water Intake

RR ............................ Red

R ............................ Revised Print

RACON .................. Radar Transponder Beacon

RAMARK ............... Radar Marker

RA Ref ................... Radar Reflector

RBN ....................... Radio Beacon

RDF ....................... Radio Direction Finder



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R E P ....................... Reported

R E S T R................... Restricted

R F.......................... Representative Fraction

RGE ....................... Range

R K ......................... Rock

R/V ........................ Research Vessel

SSAR ....................... Search and Rescue

SC ......................... Small Craft

SD ......................... Sounding Doubtful

SEC ....................... Second (time; geo pos)

SIG STA ................. Signal station

SM ......................... Statute Mile(s)

SOLAS .................. Safety of Life at Sea

SPOR .................... Shoreline Plane of Reference

S SIG STA ............. Storm Signal Station

S T .......................... Saint

STA ........................ Station

S’PIPE ................... Standpipe

S/V ........................ Sailing Vessel

TTD .......................... Time Difference

TEMP .................... Temporary

THRU ..................... Through

T R .......................... Tower

T R .......................... True

TRLB...................... Temporarily Replaced by Lighted Buoy

TRUB ..................... Temporarily Replaced by

Unlighted Buoy

TSD ....................... Time-Speed-Distance

T S S ....................... Traffic Separation Scheme

TSTM ..................... Thunderstorm

UUMIB...................... Urgent Marine Information

Broadcast

UNCOV .................. Uncovers; Dries

U S ......................... United States

USACE .................. U.S. Army Corps of Engineers

USC ....................... United States Code

USCG .................... United States Coast Guard

USCGAUX.............. United States Coast Guard

Auxiliary

USCP .................... United States Coast Pilot

USDOT .................. United States Department of

Transportation

USPHS .................. U.S. Public Health Service

U S P S .................... United States Power Squadrons

UTC ....................... Universal Coordinated Time

VVERT Cl ................. Vertical Clearance

VHF–FM ................ Very High Frequency –

Frequency Modulated

VLCTY ................... Velocity

VSBY .................... Visibility

VTC ....................... Vessel Traffic Center

VTS ....................... Vessel Traffic Services

WWEA ...................... Weather

WGS...................... World Geodetic System

WHIS ..................... Whistle

WK ........................ Wreck

W/P ....................... Watching Properly

WRNG ................... Warning

XX ............................ Discontinued Chart

YYD ......................... Yard(s)

noaa nautical chart user's manual 1997

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