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 ...
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 ...
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