Using elevation data from stereo satellite observations, David Shean is mapping the retreat of some 1,200 mountain glaciers in the continental United States. “Until recently, glaciers in the United States have been measured in two ways: placing stakes in the snow, as federal scientists have done each year since 1957 at South Cascade Glacier in Washington state; or tracking glacier area using photographs from airplanes and satellites.” Shean’s method, which measures each glacier twice a year and uses automated software to track changes, seems to cover a lot more territory. [GIS and Science]