Fractional vegetation cover for Pennsylvania was estimated from Thematic Mapper data using algorithms developed by Dr. Toby Carlson. Values range from 0 to 100, use of integer rather than decimal values reduced storage volume. Date of the imagery ranged from 1985 to 1987, availability depended on extent of cloud cover at time of acquisition. The Pennsylvania Department of Transportation supported the construction of the impervious surface data, with technical assistance from Eric Warner and Deborah Slawson.