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
- Orthorectification
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
- Gravimetry
- Physical geodesy
| Collection | DSM | DTM | Resolution | System type and data source | Availability | Coverage |
|---|---|---|---|---|---|---|
| Airbus Elevation |  | | 50 cm, 1 m, 4 m | Satellite (Pléiades Neo, Pléiades) | On demand | Global |
| Bluesky Elevation | | | 25 cm, 2 m, 5 m | Aerial (Bluesky Aerial) | On demand | UK |
| Globhe Elevation | | | 1–10 cm | Drone (Globhe Aerial and LIDAR) | On demand | Global |
| Hexagon Elevation DSM | |  | 30 cm, 60 cm | Aerial (Hexagon Aerial) | Off-the-shelf | North America and Europe |
| NEXTMap | | | 1 m, 6 m, 10 m | Aerial (SAR and LIDAR) | Off-the-shelf | Areas all over the world |
| PlanetDEM | | | 30 m | Satellite (ALOS World 3D - 30m, NASADEM) | On demand | Global |
| Vexcel Elevate | | | 5.5–7.5 cm, 15–20 cm | Aerial (Vexcel Aerial) | Off-the-shelf | Areas all over the world |
| WorldDEM Neo DSM | | | 5 m | Satellite (TerraSAR-X) | Off-the-shelf | Global* |
*The geographic coverage is global, but certain areas are restricted.
What is a vertical datum in a DEM?
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.