Chlorophyll, whether in terrestrial plants or in floating algae in lakes, has a distinct spectral signature that can be measured by satellite. This image, produced by researchers at the Environmental Remote Sensing Center (ERSC) at the University of Wisconsin-Madison using a multi-date composite of several Landsat scenes, shows algal blooms on lakes Mendota (top) and Monona (bottom right) in Madison, Wisconsin, October 31, 1999. The algae blooms appear bright green due to their particular timing. Image credit: courtesy UW-Madison Environmental Remote Sensing Center / image processing by Jon Chipman. Photo Date: 2001

Change detection techniques can help map damage areas following severe weather. This image shows, from left to right, the ground trace of an F3 tornado that touched down August 18, 2005 on the north side of Stoughton, Wisconsin. Researchers at the Environmental Remote Sensing Center (ERSC) at the University of Wisconsin-Madison produced this image for the Wisconsin Emergency Management using the blue and green spectral bands of a Landsat 5 TM image acquired one month before the storm and the red band of a Terra ASTER image acquired 10 days after the storm. Image credit: courtesy UW-Madison Environmental Remote Sensing Center / image processing by Peter Wolter / cartography by Sam Batzli. Photo Date: August 2005

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