A digital elevation model (DEM) is a representation of elevation data. DEMs are usually generated from remotely sensed data collected by satellites, drones, and planes.
A DEM can be a digital surface model (DSM) or a digital terrain model (DTM). Other derivative products of elevation models include slope, aspect, curvature, shaded relief, and normalized DSMs.
A DSM illustrates the Earth’s surface and all objects on it, while a DTM is a bare-earth model devoid of human-made and natural structures. A DTM can be derived from a DSM.
A representation of the surface of the Earth with man-made objects and vegetation.
DSMs are used for the following use cases:
- Urban planning
- Vegetation management
- Runway approach zone encroachment
A representation of the bare Earth elevation without man-made objects and vegetation.
DTMs are used for the following use cases:
- Reducing gravity measurements
- Analyzing terrain
- Physical geodesy
DEMs are referenced to a vertical datum. Depending on the model being used, a geodetic vertical datum takes a specific zero point, to which heights of various points will be referenced. The datum is needed for accurate measures of height above a surface.