USGS Gap Analysis Project Additional Data: Elevation

Some species respond to environments directly related to altitudinal variation. Elevation (e.g., DEM) is easily implemented in spatial modeling by limiting the model to the minimum and maximum values explicitly stated in the literature. DEMs are utilized directly and are measured in meters above mean sea level. The elevation dataset was derived from the National Elevation Dataset, elevation units are reported in meters. For more information regarding the National Elevation Dataset, see http://ned.usgs.gov/. This is a continuous data layer. These data are divided into 6 regions across the US (Northwest, Southwest, Great Plains, Upper Midwest, Southeast, and Northeast). If you want complete coverage of the entire US, all 6 regional files are needed. These raster data have a 30 m x 30 m cell resolution. The USGS Gap Analysis Project (GAP) GAP used the best information available to create the elevation ancillary data; however GAP seeks to improve and update these data as new information becomes available.