FAQ: What is a DEM?
What is a DEM?
A Digital Elevation Model (DEM) consists of an array of elevations for ground positions that are usually at regularly spaced intervals. The 1 degree DEM provides coverage in 1-by-1 degree blocks and is available for all of the contiguous United States, Hawaii, and most of Alaska. The 1 degree DEM consists of a regular array of elevations referenced horizontally on the geographic coordinate system of the World Geodetic System 1984 Datum. Elevation data located on the degree lines (all four sides) correspond with the same profiles on adjoining DEM blocks. Elevations are in meters relative to mean sea level.
You can obtain information about the USGS DEM data sets by calling: 800-USA-MAPS