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A digital terrain model (DTM) is a topographic model of the bare earth that can be manipulated by computer programs.
The data files contain the elevation data of the terrain in a digital format which relates to a rectangular grid. Vegetation, buildings and other cultural features are removed digitally - leaving just the underlying terrain.
DTMs are used especially in civil engineering, geodesy & surveying, geophysics, geography and remote sensing. The main applications are:
- visualization of the terrain (Block diagrams etc.)
- Calculation of project data or rock masses in civil engineering
- Reduction (terrain correction) of gravity measurements (gravimetry, physical geodesy)
- Terrain analyses in Cartography and Morphology
- Rectification of airborne or satellite photos.
The most usual grid (raster) is between 50 and 500 meters. For several applications in (1)-(3) a full resolution is required only for the central areas of the project. Therefore the huge data amount is reduced by a mix of two or three raster spacings.
In gravimetry e.g., the primary grid may be 50 m, but is switched to 100 or 500 meters in distances of about 5 or 10 kilometers.
A digital terrain model may be used to guide automatic machinery in the construction of a physical model, the relief map.
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"Digital terrain model"