A digital elevation model (DEM) is a digital representation of ground surface topography or terrain.

For the design of mobile radio networks and for the computation of the strength of the radio signal the influence of the terrain must be taken into account.In addition beside other spatial data digital elevation models are needed for the planning process.

For the production of the elevation data methods of photogrammetry and remote sensing, laser scanning, radar interferometrie as well as the digitization of qualified maps can be used.

The DEM is defined as a raster with a regular spacing in longitude and latitude direction. Each cellvalue represent the height value of the surface of the earth at the center of each pixel. 

The height values refers to a common height level, e.g. sea level of Amsterdam or Adria, and a common height system, e.g. normal heights (vertical datum).