Landsat data has also been used to map the percentage of impervious surface area of the seven-county Twin Cities Metropolitan Area in 1991, 1998 and 2000. Classification of the Landsat TM data provides a means to map and quantify the degree of impervious surface area, an indicator of environmental quality, over large areas and over time at modest cost. A regression model relating percent impervious surface area to "tasseled cap" greenness was used to estimate the percent (0 to 100%) impervious surface area for pixels classified as urban or developed.
