![Page 1: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/1.jpg)
GNSS DERIVED HEIGHTS- PART 2NOS/NGS - 59
Bill Henning
Senior Geodesist, PLS.
301-713-3196 x 111, [email protected]
NGS WEBINAR – OCTOBER 7, 2009
![Page 2: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/2.jpg)
GNSS DERIVED HEIGHTS
DAY 1
• HT MOD• GNSS HT
METHODS• NOS/NGS-58
DAY 2• NOS/NGS-59-
Baltimore County and Fairfax County
• REAL TIME HT ISSUES
![Page 3: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/3.jpg)
http://www.ngs.noaa.gov/
“NGS 59”
“NGS 58”
![Page 4: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/4.jpg)
![Page 5: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/5.jpg)
“Geoid”
PO
P
H (Orthometric Height) = Distance along plumb line (PO to P)
Earth’s
Surface
Ocean
Ellipsoid
“h = H + N”
N
h
Q
N (Geoid Height) = Distance along ellipsoid normal (Q to PO)
h (Ellipsoid Height) = Distance along ellipsoid normal (Q to P)
Plumb Line
Mean SeaLevel
H88 = h83 – N09
ELLIPSOID, GEOID & ORTHO HEIGHTS
![Page 6: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/6.jpg)
Expected Height Accuracies• GPS-Derived Ellipsoid Heights
4 2 centimeters (following NOS NGS-58 Guidelines)
• Geoid Heights (GEOID03)4 Relative differences typically less than 1 cm in
10 km4 2.4 cm RMS about the mean nationally
4 0.5 cm error in 10 Km
• Leveling-Derived Heights4 Less than 1 cm in 10 km for third-order leveling
NOAA Technical Memorandum NOS NGS-58
GUIDELINES FOR ESTABLISHING GPS-DERIVED ELLIPSOID HEIGHTS (STANDARDS: 2 CM AND 5 CM) VERSION 4.3 David B. Zilkoski Joseph D. D'Onofrio Stephen J. Frakes Silver Spring, MD November 1997 U.S. DEPARTMENT OF National Oceanic and National Ocean National Geodetic COMMERCE Atmospheric Administration Service Survey
![Page 7: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/7.jpg)
N O A A T e c h n ic a l M e m o r a n d u m N O S N G S - 5 8
G U ID E L IN E S F O R E S T A B L IS H IN G G P S - D E R IV E D E L L IP S O ID H E IG H T S( S T A N D A R D S : 2 C M A N D 5 C M )V E R S IO N 4 .3
D a v id B . Z i lk o s k iJ o s e p h D . D 'O n o f r ioS t e p h e n J . F r a k e s
S i lv e r S p r in g , M D
N o v e m b e r 1 9 9 7
U .S . D E P A R T M E N T O F N a t io n a l O c e a n ic a n d N a t io n a l O c e a n N a t io n a l G e o d e t icC O M M E R C E A t m o s p h e r ic A d m in is t r a t io n S e r v ic e S u r v e y
Available “On-Line” at
the NGS Web Site:
www.ngs.noaa.gov
SEARCH: “NGS 58”
![Page 8: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/8.jpg)
What has been accomplished using NGS 58?
• Control recovery, campaign planning/logistics• Obs schedulules, equipment checks• Observations: Repeat base lines
Different days
Different times of day (“15 hours, 27 hours”)
(Detect, remove, reduce effects due to multipath and using the same satellite geometry)
![Page 9: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/9.jpg)
FAIRFAX COUNTY HEIGHT MODERNIZATION PROJECT 2004-2006
![Page 10: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/10.jpg)
Vector Processing Accomplished• Elevation Mask - 15 degrees
• Ephemeris - Precise (typ. 14 days latency)
• Tropospheric Correction Model
• Iono Corrections - All baselines longer than 5 km.
• Fix Integers
Baselines less than 5 km: L1 fixed solution
Baselines greater than 5 km: Iono free (L3) solution
• Baselines must have RMS values ≤ 1.5 cm• Baselines must have difference in “up” ellipsoid
height ≤ 2.0 cm
![Page 11: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/11.jpg)
From To Session dh Diff Dist RMS Solution Station Station Meters cm Meters Type
BM20 04KU 076G 46.009 3628 0.015 L1 fixed double 077G 46.004 0.5 0.017 L1 fixed double 078R* 46.007 0.2 0.015 L1 fixed double ZINC PT14 078A 15.397 3173 0.006 L1 fixed double 077A 15.400 0.3 0.006 L1 fixed double 076A 15.408 1.1 0.006 L1 fixed double TIDE 04KU 078G 43.680 3133 0.022 L1 fixed double 077R* 43.654 2.6 0.024 L1 fixed double 076R* 43.658 2.2 0.020 L1 fixed double PT14 TIDE 077A -55.031 3765 0.022 L1 fixed double 078R* -55.027 0.4 0.023 L1 fixed double 076R* -55.019 1.2 0.018 L1 fixed double 04KU 5144 078G 28.939 7250 0.014 Iono free fixed 077G 28.947 -0.8 0.014 Iono free fixed 076G 28.940 -0.1 0.020 Iono free fixed 5144 ZINC 078A -33.045 6167 0.011 Iono free fixed 077A -33.051 -0.6 0.009 Iono free fixed 076A -33.063 -1.8 0.013 Iono free fixed
*NOTE - Reprocessed vectors which had differences greater than 2 cm.
Repeat Vector Analysis After Re-Processing
![Page 12: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/12.jpg)
Adjustment Procedures to Obtain GPS-Derived NAVD’88 Orthometric Heights
![Page 13: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/13.jpg)
Least Squares Adjustments
• The adjustment minimizes the effects of random errors
• A least squares adjustment computes a single network solution, even with redundant vectors
• Least squares will highlight blunders and large errors
• It will provide estimates on the precision of the coordinates for the stations
![Page 14: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/14.jpg)
• HARN/Control Stations• (75 km)
• Primary Base• (40 km)
• Secondary Base• (15 km)
• Local Network Stations• (7 to 10 km)
• GPS ELLIPSOID HEIGHT HIERARCHY
![Page 15: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/15.jpg)
Project Adjustment Following Guidelines
CORSHARNNAVD’88 BMNew Station
121°40’W122°35’W
37°50’N
38°20’N
LA
TIT
UD
E
LONGITUDE
Spacing StationPrimary Base Station
8.2km
![Page 16: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/16.jpg)
Adjustment of Primary Network Stations From Control
Horizontal Adjustment(Latitude, Longitude, Ellipsoid Heights)
• Minimum Constrained [One fixed station]4 Fix latitude, longitude and ellipsoid height at one station4 Resolve all blunders and large residuals4 Determine which Control and known Primary Base
Station coordinates should be fixed
• Constrained [All suitable stations fixed]4 Fix latitude, longitude, and ellipsoid heights at Control
and known Primary Base Stations4 Make sure the constraints did not distort the project
NOTE - Geoid model NOT applied at this time
![Page 17: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/17.jpg)
FAIRFAX COUNTY
CONTROL & PRIMARY STATIONS
![Page 18: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/18.jpg)
CORSHARNNAVD’88 BMNew Station
121°40’W122°35’W37°50’N
38°20’N
LA
TIT
UD
E
LONGITUDE
Primary Base Station
Adjustment of Primary Base Stations
MOLAMART
LAKE
10CCD191
29.6km25.8km
38.7
km
19.0km
28.7km
25.7km 38.3km
31.6
km• CORS, Control Points (known Primary Control) horizontal
• latitude, longitude, and ellipsoid heights• No NAVD88 orthometric heights constrained at this time
Constrained Horizontally
![Page 19: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/19.jpg)
Adjustment of Local Network Stations
Horizontal Adjustment(Latitude, Longitude, Ellipsoid Heights)
• Minimum Constrained [One fixed station]4 Fix latitude, longitude and ellipsoid height at one station4 Resolve all blunders and large residuals4 Evaluate coordinates at Control and Primary Base
Station» should not be greatly affected by Local Station
baselines
• Constrained [All suitable stations fixed]4 Fix latitude, longitude, and ellipsoid heights at Control
and Primary Base Stations4 Make sure the constraints did not distort the project
NOTE - Geoid model NOT applied at this time
![Page 20: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/20.jpg)
CORSHARNNAVD’88 BMNew StationSpacing Station
121°40’W122°20’W37°55’N
38°16’N
LA
TIT
UD
E
LONGITUDE
Primary Base Station
8.2km
Adjustment of Local Network Stations
• Existing and newly derived Primary Control horizontal• latitude, longitude, and ellipsoid heights
• No NAVD88 orthometric heights constrained at this time
Constrained Horizontally
![Page 21: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/21.jpg)
Combined Network Horizontal Adjustment
• Perform combined adjustment
4 Control and Primary Base network along with local network
4 Latitude, longitude, and ellipsoid height
• Use GEOID model to obtain geoid heights
• Make sure combined adjustment did not distort the project
![Page 22: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/22.jpg)
Combined Horizontal AdjustmentCORSHARNNAVD’88 BMNew Station
121°40’W122°35’W
37°50’N
38°20’N
LA
TIT
UD
E
LONGITUDE
Spacing StationPrimary Base Station
8.2km
• CORS, Control Points and existing and new Primary Control horizontal• latitude, longitude, and ellipsoid heights
• No NAVD88 orthometric heights constrained at this time
Constrained Horizontally
![Page 23: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/23.jpg)
FAIRFAX HORIZONTAL
![Page 24: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/24.jpg)
BASELINE ADJUSTMENT SUMMARY
![Page 25: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/25.jpg)
From To Session dh Diff Dist RMS Solution Station Station Meters cm Meters Type
BM20 04KU 078G 45.974* 3628 0.016 L1 float double 077G 46.004 -3.0 0.017 L1 fixed double 076G 46.009 -3.5 0.015 L1 fixed double ZINC PT14 078A 15.397 3173 0.006 L1 fixed double 077A 15.400 0.3 0.006 L1 fixed double 076A 15.408 1.1 0.006 L1 fixed double TIDE 04KU 078G 43.680 3133 0.022 L1 fixed double 077G 43.654* 2.6 0.024 L1 fixed double 076G 43.607* 7.3 0.020 L1 fixed double PT14 TIDE 078A -54.703* 3765 0.047 L1 fixed double 077A -55.031 -32.8 0.022 L1 fixed double 076A -55.007* -30.4 0.019 L1 fixed double 04KU 5144 078G 28.939 7250 0.014 Iono free fixed 077G 28.947 -0.8 0.014 Iono free fixed 076G 28.940 -0.1 0.020 Iono free fixed 5144 ZINC 078A -33.045 6167 0.011 Iono free fixed 077A -33.051 -0.6 0.009 Iono free fixed 076A -33.063 -1.8 0.013 Iono free fixed
Repeat Vector Analysis
*NOTE - Reprocess all vectors which have difference greater than 2 cm.
![Page 26: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/26.jpg)
Guidelines for Establishing
GPS-Derived OrthometricHeights
(Standards: 2 cm and 5 cm)
http://www.ngs.noaa.gov/
SEARCH: “NGS 59”
![Page 27: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/27.jpg)
• Three Basic Rules
• Four Basic Control Requirements
• Five Basic Procedures
3-4-5 System
A Guide for Establishing GPS-Derived Orthometric Heights(Standards: 2 cm and 5 cm)
![Page 28: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/28.jpg)
Three Basic Rules
• Rule 1:4 Follow NGS’ guidelines for establishing GPS-derived
ellipsoid heights (NGS 58:Standards: 2 cm and 5 cm)
• Rule 2:4 Use latest National Geoid Model, i.e., GEOID09
• Rule 3:4 Use latest National Vertical Datum, i.e., NAVD 88
![Page 29: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/29.jpg)
FOUR BASIC CONTROL REQUIREMENTS
• BCR-1: Occupy stations with known NAVD 88 orthometric heights4 Stations should be evenly distributed throughout project
• BCR-2: Project areas less than 20 km on a side, surround project with NAVD 88 bench marks4 i.e., minimum number of stations is four; one in each corner of
project
• BCR-3: Project areas greater than 20 km on a side, keep distances between GPS-occupied NAVD 88 bench marks to less than 20 km
• BCR-4: Projects located in mountainous regions, occupy bench marks at base and summit of mountains, even if distance is less than 20 km
![Page 30: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/30.jpg)
BCR1: Sketch indicates that
the 20 km rule was met.
BCR2: This requirement is not applicable because the project is greater than 20 km on a side.
BCR4: This requirement is not applicable because project is not in a mountainous region.
BCR Example
BCR3: Circled bench marks are mandatory. Analysis must indicate bench marks have valid
NAVD 88 heights. Other BMs can be substituted but user must adhere to 20 km requirement.
![Page 31: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/31.jpg)
FAIRFAX COUNTY VERTICALS USED
40 KM
![Page 32: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/32.jpg)
Five Basic Procedures
• BP-1: Perform 3-D minimum-constraint least squares adjustment of GPS survey project4 Constrain 1 latitude, 1 longitude, 1 orthometric height
(Recall that ellipsoid heights have already been analyzed and adjusted)
• BP-2: Analyze adjustment results from BP-14 Detect and remove all data outliers
![Page 33: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/33.jpg)
After performing minimum constraint adjustment, plot ellipsoid height residuals (or dU residuals) and investigate all residuals greater than 2 cm.
![Page 34: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/34.jpg)
Station pairs with large residuals, i.e., greater than 2.5 cm, also have large repeat base line differences. NGS guidelines for estimating GPS-derived ellipsoid heights require user to re-observe these base lines. Following NGS guidelines provides enough redundancy for adjustment process to detect outliers and apply residual on appropriate observation, i.e., the bad vector.
![Page 35: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/35.jpg)
• BP-3: Compute differences between GPS-derived orthometric heights from minimum-constraint adjustment in BP-2 and published NAVD88 orthometric heights for all known bench marks
Five Basic Procedures(continued)
![Page 36: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/36.jpg)
CONTROL COMPARISON
OUTLIERS?
• PASSIVE CONTROL QUALITY (OVER TIME)
• GEOID MODEL QUALITY
![Page 37: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/37.jpg)
GPS-Derived Orthometric Heights Minus NAVD88 Heights
All height differences are under 5 cm and most are less than 2 cm. Almost all relative height differences between adjacent station pairs are less than 2 cm. However, most of the height differences appear to be positive relative to the southwest corner of the project.
Geoid99Units = Centimeters
![Page 38: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/38.jpg)
Five Basic Procedures(continued)
• BP-4: Determine which BMs have valid NAVD88 height values from results from BP-34 Differences need to agree 2 cm for 2 cm survey4 Differences need to agree 5 cm for 5 cm survey4 May detect systematic tilt over large areas
» Solve for geoidal slope and scale
• BP-5: Perform constrained adjustment with results from BP-44 Constrain 1 latitude, 1 longitude, all valid orthometric
height values4 Ensure final heights not distorted in adjustment
![Page 39: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/39.jpg)
To detect and remove any systematic trend, a tilted plane is best fit to the height differences (Vincenty 1987, Zilkoski and Hothem 1989). After a trend has been removed, all the differences are less than +/- 2 cm except for one and almost all relative differences between adjacent stations are less than 2 cm.
GPS-Derived Orthometric Heights Minus NAVD88 Heights
Geoid99Units = Centimeters
![Page 40: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/40.jpg)
After rejecting the largest height difference (-2.4 cm), of all the closely spaced station pairs only 3 are greater than 2 cm, 1 is greater than 2.5 cm and none are greater than 3 cm.
GPS-Derived Orthometric Heights Minus NAVD88 Heights
Geoid99Units = Centimeters
![Page 41: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/41.jpg)
The stations in blue designated as "Height Mod" in the NGS Integrated Database
The red stars are the CORS used in the "Height Mod" projects.
![Page 42: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/42.jpg)
Elevation published
to centimeters
Orthometric height
determined by GPS
Identified as Height Mod
survey station
![Page 43: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/43.jpg)
Topography
AB
C
D
E
F
GPS-Derived Heights from GEOID03 Separation
= Published NAVD88 Orthometric Height = New Control
Ellipsoid
hh
hh
hh
GEOID03
N NN N
NN
Hh-N
Hh-NHh-N
Hh-N
Hh-N
Hh-N
![Page 44: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/44.jpg)
Constrained Vertical Adjustment
Topography
AB
C
D
E
F
hadj
hadjhadj
hadj
hadj
hadj
AdjustedEllipsoid
Ellipsoid Height Adjusted to Fit Constrained Orthometric Heights
GPS-Derived Orthometric Heights
= Published NAVD88 Orthometric Height = New Control
H
HH
H
Geoid based on Ortho Heights
GEOID03
Ellipsoid
hh
hh
hhHGPS
HGPS
N NN N
NN
GEOID03
![Page 45: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/45.jpg)
ADJUSTMENT TO PASSIVE CONTROL
![Page 46: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/46.jpg)
3-D Vertical Adjustment(Orthometric Heights)
• Minimum Constrained [One fixed station]4 Fix latitude, longitude, and orthometric height at one station4 Resolve all blunders and large residuals4 Compare orthometric heights from adjustment with published
NAVD 884 Determine which NAVD 88 bench marks should be fixed
• Constrained [All suitable orthometric heights fixed]4 Fix latitude, longitude at one station4 Fix orthometric heights at all suitable stations4 Make sure the constraints did not distort the project
Combined Network Vertical Adjustment
![Page 47: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/47.jpg)
Minimally Constrained Vertical Adjustment
• 1 horizontal latitude and longitude• 1 NAVD88 orthometric heights
CORSHARNNAVD’88 BMNew Station
121°40’W122°35’W
37°50’N
38°20’N
LA
TIT
UD
E
LONGITUDE
Spacing StationPrimary Base Station
8.2km
Constrained Vertically
![Page 48: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/48.jpg)
Constrained Vertical Adjustment
• 1 horizontal latitude and longitude• All valid NAVD88 orthometric heights
CORSHARNNAVD’88 BMNew Station
121°40’W122°35’W
37°50’N
38°20’N
LA
TIT
UD
E
LONGITUDE
Spacing StationPrimary Base Station
8.2km
Constrained Vertically
![Page 49: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/49.jpg)
NGS Data Sheet - GEOID03Published NAVD88 to GPS Derived
HT2268 DESIGNATION - S 1320 HT2268 PID - HT2268 HT2268 STATE/COUNTY- CA/SAN FRANCISCO HT2268 USGS QUAD - SAN FRANCISCO NORTH (1975) HT2268 HT2268 *CURRENT SURVEY CONTROL HT2268 ___________________________________________________________________ HT2268* NAD 83(1992)- 37 45 25.30727(N) 122 28 36.34687(W) ADJUSTED HT2268* NAVD 88 - 102.431 (meters) 336.06 (feet) ADJUSTED HT2268 ___________________________________________________________________ HT2268 EPOCH DATE - 1997.30 HT2268 X - -2,711,121.437 (meters) COMP HT2268 Y - -4,259,419.310 (meters) COMP HT2268 Z - 3,884,200.262 (meters) COMP HT2268 LAPLACE CORR- 5.53 (seconds) DEFLEC03 HT2268 ELLIP HEIGHT- 69.78 (meters) GPS OBS HT2268 GEOID HEIGHT- -32.60 (meters) GEOID03 HT2268 DYNAMIC HT - 102.363 (meters) 335.84 (feet) COMP HT2268 MODELED GRAV- 979,964.0 (mgal) NAVD 88 HT2268 HT2268 HORZ ORDER - FIRST HT2268 VERT ORDER - FIRST CLASS I HT2268 ELLP ORDER - FOURTH CLASS I HT2268
H =102.431 =
102.431 102.38 102.429! GEOID 09
69.78- (-32.60)- Nh
GEOID96 = 0.17 m
GEOID99 = 0.11 m
GEOID03 = 0.05 m
GEOID 09 = 0.002 m
![Page 50: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/50.jpg)
SUMMARY• Mistakes and systematic errors must be removed
before the adjustment
• A least squares adjustment handles random errors and provides a single solution (Try to eliminate all systematic errors)
• The Minimally Constrained adjustment checks the internal consistency of the network
• The Constrained adjustment checks the existing control and references the network to the datum
• The vertical adjustment estimates GPS-derived Orthometric heights- Approaching 3rd order leveling accuracies
![Page 51: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/51.jpg)
ORTHOMETRIC HEIGHTS FROM REAL TIME GNSS POSITIONING
• NAD 83 ELLIPSOID + NGS HYBRID GEOID MODELOR
• LOCK TO PASSIVE MONUMENTATION (INCLINED PLANE + NGS HYBRID GEOID MODEL)OR
• DIFFERENCE IN ELLIPSOID HEIGHTS FOR ≤ 10 Km
![Page 52: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/52.jpg)
REAL TIME GNSS POSITIONING USERS GUIDELINES
![Page 53: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/53.jpg)
>200 RTN WORLD WIDE
>80 RTN IN USA
35+ STATE DOT
MANY COOP EFFORTS
![Page 54: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/54.jpg)
SUMMARY TABLE FROM THE SINGLE-BASE GUIDELINES
![Page 55: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/55.jpg)
BEST METHODS FROM THE GUIDELINES:THE 7 “C’S” of NOAA’s NGS
• CHECK EQUIPMENT• COMMUNICATION• CONDITIONS• CALIBRATION (OR NOT)• COORDINATES• COLLECTION• CONFIDENCE
• THE CONTROL IS AT THE POLE
http://www.ngs.noaa.gov/PUBS_LIB/NGSRealTimeUserGuidelines.v2.0.4.pdf
http://www.ngs.noaa.gov/SEARCH: “CLASSICAL REAL TIME”
![Page 56: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/56.jpg)
METADATA• BESIDES ATTRIBUTE FIELDS, THE RT PRACTICIONER
MUST KEEP RECORDS OF ITEMS NOT RECORDED IN THE FIELD,FOR INSTANCE:
WHAT IS THE SOURCE OF THE DATA? WHAT IS THE DATUM/ADJUSTMENT/EPOCH? WHAT ARE THE FIELD CONDITIONS? WHAT EQUIPMENT WAS USED, ESPECIALLY- WHAT
ANTENNA? WHAT FIRMWARE WAS IN THE RECEIVER &
COLLECTOR? WHAT REDUNDANCY, IF ANY, WAS USED?
![Page 57: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/57.jpg)
QUICK FIELD SUMMARY:
• Set the base at a wide open site• Set rover elevation mask between 12° & 15°• The more satellites the better• The lower the PDOP the better• The more redundancy the better• Beware multipath• Beware long initialization times• Beware antenna height blunders• Survey with “fixed” solutions only• Always check known points before, during and after new location sessions• Keep equipment adjusted for highest accuracy• Communication should be continuous while locating a point• Precision displayed in the data collector can be at the 68 percent confidence level,
which is only about half the error spread to get 95 percent confidence• Have back up batteries & cables• RT doesn’t like tree canopy or tall buildings
• Set the base at a wide open site• Set rover elevation mask between 12° & 15°• The more satellites the better• The lower the PDOP the better• The more redundancy the better• Beware multipath• Beware long initialization times• Beware antenna height blunders• Survey with “fixed” solutions only• Always check known points before, during and after new location sessions• Keep equipment adjusted for highest accuracy• Communication should be continuous while locating a point• Precision displayed in the data collector can be at the 68 percent confidence level,
which is only about half the error spread to get 95 percent confidence• Have back up batteries & cables• RT doesn’t like tree canopy or tall buildings
![Page 58: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/58.jpg)
THE QUICK SUMMARY BOILED DOWN:• COMMUNICATIONS: THE KEY TO SUCCESS
• CHECK SHOT: FIRST BEFORE NEW WORK
• REDUNDANCY: FOR CONFIDENCE
![Page 59: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/59.jpg)
CONSTRAINING PASSIVE MARKS
![Page 60: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/60.jpg)
CALIBRATIONS/VERTICAL LOCALIZATIONS
![Page 61: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/61.jpg)
USING OPUS-S OR OPUS –RS WITH REAL TIME POSITIONING FOR
SMALL PROJECTS
![Page 62: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/62.jpg)
![Page 63: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/63.jpg)
![Page 64: GNSS DERIVED HEIGHTS DAY 1 HT MOD GNSS HT METHODS NOS/NGS-58 DAY 2 NOS/NGS-59- Baltimore County and Fairfax County REAL TIME HT ISSUES](https://reader030.vdocuments.site/reader030/viewer/2022032723/56649d0b5503460f949df6a0/html5/thumbnails/64.jpg)
GNSS DERIVED HEIGHTS Summary of expected orthometric
precisions/accuraciesREMEMBER REDUNDANCY AND A CHECK ON KNOWN
POINTS• CORS = 0.05 m
• OPUS-S = 0.05 m
• OPUS-RS = 0.05 m
• NGS 58/59 = 0.02 m local, 0.05 m to NSRS
• SINGLE BASE REAL TIME = 0.02 m ≤ 10 Km, remember GIGO
• RTN = 0.03- 0.05 m,