Digital Terrain Models (DEM – DTM – DSM)

Digital Terrain Model - Digital Surface Model

A Digital Elevation Model (DEM) is a 3D representation of the earth’s surface terrain elevations, and is the most common basis for digitally produced relief maps. A DEM can be represented either as a raster or as a vector-based triangular irregular network (TIN), and they are generated from variably-spaced LiDAR ground points. When DEM data are further enhanced with breaklines, containing additional information of the terrain in areas where LiDAR is unable to efficiently map the ground, a Digital Terrain Model (DTM) is produced. In contrast to a Digital Surface Model (DSM) which contain objects like vegetation, buildings and powerlines, the DTM represents only the bare ground surface. Common uses of DEMs include amongst others modelling of water flow for hydrology or mass movement (e.g. avalanches and landslides), terrain and surface analysis in geomorphology, archaeology, precision farming and forestry, or to support specialized applications such as volumetric calculations, 3D modelling and powerline as-built surveys. Simultaneously fully detailed DTMs are utilized for contour generation, flood plain mapping and rectification of aerial photography or satellite imagery.

Airborne 3D laser scanning is the only surveying method that can provide sufficiently dense elevation data of forested terrain, mapping with great accuracy (i.e. multiple points per square meter) the ground beneath forests. High-resolution terrain (DTM) and surface (DSM) models are created by applying class filtering to return pulses, and are available with regard to customers’ exact specifications. Digital models of terrain surfaces and object surfaces (e.g. bare earth, city models, vegetation models) can be provided in different grid sizes for a large variety of applications. We apply rigorous quality-control procedures along each step of the processing way, and required corrections are made to the models when needed.