The USGS Digital Elevation Model (DEM) data files are digital representations of cartographic information in a raster form. DEMs consist of a sampled array of elevations for a number of ground positions at regularly spaced intervals. The DEM data for 7.5-minute units correspond to the USGS 1:24,000- and 1:25,000-scale topographic quadrangle map series for all of the United States and its territories. Each 7.5-minute DEM is based on 30- by 30-meter data spacing with the Universal Transverse Mercator (UTM) projection. Each 7.5- by 7.5-minute block provides the same coverage as the standard USGS 7.5-minute map series. The UTM-based 7.5-minute DEM data are available for most of the contiguous United States, Hawaii, and Puerto Rico.