TNM data (elevation and land cover) have been used to develop a national inventory of significant topographic changes in the U.S. TNM elevation data (National Elevation Dataset) and Shuttle Radar Topography Mission (SRTM) data form a unique pair of seamless multi-temporal elevation datasets that were analyzed to detect 20th century topographic surface changes. An extensive Web site ( http://topochange.cr.usgs.gov/ ) details the project. An interactive viewer ( http://topochange.cr.usgs.gov/TopoChange_viewer/viewer.htm ) allows viewing, query, and download of the topographic change inventory and selected TNM layers.
Idea No. 21