Some species respond to the amount of canopy cover within a habitat type. The Percent Canopy Cover dataset was derived from the National Land Cover Dataset. The canopy cover database was compiled from the National Land Cover Dataset, and classifies each pixel into 101 possible values (0% - 100%). The canopy density estimate applies to the forest classes only. For further information on Canopy Cover, see http://landcover.usgs.gov/pdf/canopy_density.pdf. This dataset is a continuous canopy cover percentage and cover the entire U.S. These raster data have a 30 m x 30 m cell resolution. The USGS Gap Analysis Project (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.