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
A digital elevation model that blends DSM and DTM characteristics by leveling small objects and urban structures to approximate bare earth, while retaining larger vegetation and terrain features with moderate smoothing. Hybrid DEMs are used for the following use cases:
- Orthorectification
- Terrain modeling
- Cartographic mapping
- Environmental monitoring
| Collection | Model type | Resolution | System type and data source | Availability | Coverage |
|---|---|---|---|---|---|
| Airbus Elevation | DSM DTM | 50 cm, 1 m, 4 m | Satellite (Pléiades Neo, Pléiades) | Upon request | Global |
| Bluesky Elevation | DSM DTM | 25 cm, 2 m, 5 m | Aerial (Bluesky Aerial) | Upon request | UK |
| Globhe Elevation | DSM DTM | 1–10 cm | Drone (Globhe Optical and LIDAR) | Upon request | Global |
| Hexagon Elevation DSM | DSM | 30 cm, 60 cm | Aerial (Hexagon Aerial) | Off-the-shelf | North America and Europe |
| NEXTMap | DSM DTM | 1 m, 6 m, 10 m | Aerial (SAR and LIDAR) | Off-the-shelf | Areas all over the world |
| PlanetDEM | DSM | 30 m | Satellite (ALOS World 3D - 30m, NASADEM) | Upon request | Global |
| Vexcel Elevate | DSM DTM | 5.5–7.5 cm, 15–20 cm | Aerial (Vexcel Aerial) | Off-the-shelf | Areas all over the world |
| WorldDEM Neo | DSM DTM | 5 m | Satellite (TerraSAR‑X) | Off-the-shelf | Global* |
| WorldDEM4Ortho | Hybrid | 24 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.