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What is the projection, horizontal datum, vertical datum, and resolution for a USGS digital elevation model (DEM)?

Projection:  3DEP DEMS have different projections/coordinate systems depending on the product:

  • 1/3-, 1-, and 2-arc-second (also the discontinued 1/9-arc-second) DEMs are not projected.  They are all in geographic coordinates (latitude/longitude).
  • 5-meter DEMs (Alaska only) are Alaska Albers Equal Area.
  • 1-meter DEMs are in Universal Transverse Mercator (UTM).
  • Original Product Resolution (OPR) DEMs – projection varies.
  • The coordinate system and projection information for ALL DEMs are in each DEM file header; GIS software should detect them automatically.

Horizontal Datum:  The North American Datum of 1983 (NAD83)  

Vertical Datum:  Typically the North American Vertical Datum of 1988 (NAVD88), although the National Geodetic Vertical Datum of 1929 (NGVD29) and local reference datums are used in some areas outside of the conterminous United States. For Hawaii, Puerto Rico, U.S. Virgin Islands, and Pacific Island territories, the vertical datum is typically referenced to local mean sea level.    

Resolution:  The conterminous United States is available at horizontal resolutions of  

  • 1-arc-second (~30 meters):  full coverage  
  • 1/3-arc-second (~10 meters): full coverage   
  • 1/9-arc-second (~3 meters): partial coverage  
  • 1-meter: partial coverage   

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