![]() Coverage is complete at 30-meter resolution. The resolution of a DEM is a function of the east-west spacing of the profiles and the south-north spacing of elevation points within each profile.ĭEMs corresponding to 7.5-minute quadrangles are available at 10-meter resolution for much, but not all, of the U.S. Large-scale (7.5-minute and 15-minute), intermediate scale (30 minute), and small-scale (1 degree) series were produced for the entire U.S. Like other USGS data, DEMs were produced originally in tiles that correspond to topographic quadrangles. USGS DEMs are raster grids of elevation values that are arrayed in series of south-north profiles. ![]() Later in this chapter, we'll consider sources of global terrain data. Here we consider the characteristics of traditional DEMs produced by the USGS. The NED has been incorporated into a newer elevation data product at the USGS called the 3D Elevation Program (3DEP). Geological Survey produced a nation-wide DEM called the National Elevation Dataset (NED), which has traditionally served a primary source of elevation data. In general, a DEM is any raster representation of a terrain surface.
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