A file with .dem extension is a mapping file that represents elevation (height) data as terrain in 3D computer graphics. Common example of such data is the terrain of earth that includes mountains, plain land, and sea depths. DEM files are commonly used by Geographic Information Systems (GIS) to produce digital elevation maps. Information stored in DEM files also includes large-scale topographic relief information that is used in earth sciences, resource management, land planning, surveying, and engineering projects. Information about land XYZ is placed at regular grid-spaced intervals for ground relief representation.
DEM File Format - More Information
Internal details of DEM files are not available publicly for developer’s reference. However, DEM files can have different file formats such as:
Bathymetric Attributed Grid (BAG)
DIMAP Sentinel 1 ESA data base
Where to find DEM files?
DEM files are commonly available on the internet and samples can be downloaded for use. The United States Geological Survey (USGS) provides many DEM files at their web site.