Quadrilateral Data Structure

Geodetic latitudeand longitude onGRS80/WGS 84ellipsoid(NAD 83)

Grid cell resolutionconstant N-S butprogressively finer E-W resolution fromequator to pole

ETOPO5 Global Digital Elevation Model

ETOPO5 Digital Elevation Model(DEM)

Row Major Order

World Map (left) made from World Map (left) made from ETOPO5 DEMETOPO5 DEM

ETOPO2 Global DEMfrom National Geophysical Data Center

Piece of a World Map Piece of a World Map made from ETOPO2 DEMmade from ETOPO2 DEM

Worldwide Land And Worldwide Land And Sea Elevation DataSea Elevation Data

In MetersIn Meters(3.7x3.7km cells at equator)(3.7x3.7km cells at equator)

Technical Specifications(0,0) (10799,0)

(0,5399) (10799,5399)

Row Major Order

))

Technical Specifications(0,0) (10799,0)

(0,5399) (10799,5399)

2-byte signed integer data5400 rows by 10800

columns116,640,000 byte dataset

Row Major Order

ETOPO1 Global DEMfrom National Geophysical Data Center

Worldwide Land And Worldwide Land And Sea Elevation DataSea Elevation Data

In MetersIn Meters(1.85x1.85km cells at equator)(1.85x1.85km cells at equator)

Technical Specifications(0,0) (21599,0)

(0,10799) (21599,10799)

Row Major Order

Technical Specifications(0,0) (21599,0)

(0,10799) (21599,10799)

Row Major Order

2-byte signed integer data10800 rows by 21600

columns466,560,000 byte dataset

Map made from ETOPO1 dataMap made from ETOPO1 data

GLOBE 30” x 30” Global Land DEM

Globe 30” x 30” grid cell data structure and tiling, format, and dataset size

Alaska Map Made From Globe Data

STRM30 Plus

NGDC 3 Arc-Second Coastal Relief Model

Map madeFrom CoastalRelief Model

National Elevation Dataset (NED)

One-second Grid For All U.S. States except…

Two-second Grid For Alaska

National Elevation Dataset (NED)Data Format and Tiling Scheme

Web Mapping Using NED 1” x 1” Data

National Elevation Dataset (NED)

1/3rd and 1/9th second Grids For Certain Areas

1/3rd Second Maps for Monterey

1/3rd Second Maps for Monterey

Ordering SRTM Data

Data Products

Shuttle Radar Topography Mission (SRTM)

SRTM Data Completeness Problems

Map Projection-basedRaster Data

USGS 7.5’x7.5’ 10m DEMs for Oregon

USGS 7.5’x7.5’ 10m DEMs for Oregon

Available only inSDTS Format

USGS 1:24000-scale Digital Raster

Graphics (DRG)

scanned topographic maps of U.S. states

and territories

Scanned at250 dpi

USGS 1 km Global Land Cover Characteristics database (GLCC)

Classified 1km x 1 kmAVHRR satellite data

Gridded on Interrupted Goode

Homolosine and Lambert Equal Area Map Projection Surfaces

Now in 30 arc second Quadrilateral Form

Several Land CoverClassification Systems Used