DEM

DEMs (Digital Elevation Models) data) are digital representations of geographic information that are in raster format and are made up of arrays of regularly spaced elevation values which are referenced horizontally to a geographic coordinate system. The USGS makes maps using five types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM. The USGS collects DEM data by interpolation from vectors or digital line graph (DLG) hypsographic and hydrographic data. This image is an X-band DEM of Oetztal, Austria, located in the Central Alps at the border between Switzerland, Italy, and Austria. It was acquired by imaging radar aboard the space shuttle Endeavour in 1994. The Gepatschferner glacier seen at the left of the image center is in light blue.