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What are digital elevation models (DEMs)?

USGS Digital elevation models (DEMs) are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The USGS acquires bare-earth elevation source data through the 3DEP Elevation Program and resamples the data to several National Map DEM products for the U.S. and territories.  The DEM products include 2, 1, 1/3, and 1/9 arc-second layers, as well as 5-meter DEMs in Alaska and 1-meter DEMs in the conterminous U.S.  The 2, 1, and 1/3 arc-second DEMs are logically seamless terrain surfaces in their respective areas of coverage and are produced from the highest quality elevation data held by the USGS.

Tags: Maps, Topographic, Data Products