What are 3" Digital Elevation Models (DEMs)?

A Digital Elevation Model (DEM), consists of a sampled array of elevations for ground positions that are normally at regularly spaced intervals. The 1-Degree DEM (3- by 3-arc-second data spacing) provides coverage in 1- by 1-degree blocks for all of the contiguous United States, Hawaii, and limited portions of Alaska. The basic elevation model is produced by or for the Defense Mapping Agency (DMA), but is

distributed by the USGS, EROS Data Center, in the DEM data record format. In reformatting the product the USGS does not change the basic elevation information. 1-degree DEM's are also referred to as "3-arc second" or "1:250,000 scale" DEM data.

Once imported into ArcInfo, these DEMs can be used for watershed delineation, stream network delineation, and hydrologic analysis. For more information on the hydrologic uses of DEMs, see the AML entitled Watershed Delineation.

Go to 3" DEM Web Site

Go to Obtaining Hydrologic Data through the Internet