Digital Elevation Model
Digital Elevation Models (DEMs) consist of a raster grid of regularly spaced elevation values that have been primarily derived from the USGS topographic map series. Elevation data on this CD-ROM are from theUSGS National Elevation Dataset (NED). The NED is a seamless raster dataset developed by merging the highest-resolution, best-quality 1:24,000-scale Digital Elevation Model (DEM) data available across the United States. From this DEM, a shaded relief model was created and is available in the DEM folder as well.