Night space images show development

From Philadelphia, at a meeting of the Association of American Geographers

For many emergency-management officials, monitoring the rapid pace of development in fire-prone regions of the western United States is a daunting task. Now, scientists may have come up with a means to estimate population growth in these areas by using satellite images taken at night.

To assess the fire risk to people in a region, analysts need to determine where houses are being built and how close they are to each other. However, by the time enough data are compiled by current methods, the information is often already outdated, says Thomas J. Cova, a geographer at the University of Utah in Salt Lake City. For example, census data in most sparsely populated areas of the United States are updated only once every 10 years. Acquiring and assembling data for broad regions can be difficult if not impossible, says Cova.

To circumvent these troubles, emergency-response officials have sometimes resorted to high-resolution daytime satellite images. But these are expensive, and analyzing them to spot houses in thickly forested areas is tedious. Cova and his colleagues suggest that analysts can more easily spot areas with booming populations by compiling and analyzing nighttime images taken by Defense Department satellites. They carry instruments sensitive enough to detect the illumination from a single floodlight outside a home at night.

By comparing such composite images of Colorado snapped in 2000 with images gathered in 1992, the team estimated the rates of development in many areas. In Teller County, the acreage developed jumped by the most, 7.3 percent.

Such data are next combined with maps that depict a region’s fire hazard, assigned on the basis of factors such as terrain and types of vegetation. Analysts can then estimate the fire risk to specific locales.