No audio available for this content. Topobathymetric digital elevation model of the confluence of the Potomac and Shenandoah Rivers at Harper’s Ferry, West Virginia. (Image: USGS) The United States ...
A digital map of the elevation of an area on the earth. The data are either collected by a private party or purchased from an organization such as the U.S. Geological Survey (USGS) that has already ...
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