Refining 1970's Land-Use Data With 1990 Population Data To Indicate New Residential Development

摘要

A procedure using a geographic information system was developed to define urban land use representative of the 1990s by overlaying U.S. Bureau of the Census 1990 population density at the block group level on 1970's digital land-use data from 1:250,000- and 1:100,000-scale maps. Any area having a population density of 1,000 or more people per square mile is re-classified as urban land use in the derivative product. The procedure was applied to 20 study units of the National Water-Quality Assessment program to provide what are considered reasonable indications of urbanization that has occurred since the 1970s.