DEM - USA

http://www.math.montana.edu/~nmp/materials/ess/rs/index4.html

A Digital Elevation Model (DEM) is a dataset containing elevation values either in rasterized data form or in a Triangular Irregular Network (TIN).  These datasets are commonly created through remote sensing techniques but can also be made through land surveying.  This data is commonly used in a GIS and is the basis for relief maps.

The above image is a DEM of the contiguous United States.  Through this DEM we can see the commonly known mountain ranges of the U.S.   The rocky mountains are visible in the Western U.S. and the Appalachain mountains are visible along the east coast.