Digital Elevation Models (DEMs)
A Digital Elevation Model (DEM) is a collection of discrete elevation points at regularly spaced intervals. The model reflects abrupt changes in relief such as incised streams, ridge lines, and slope breaks.
The Two Methods to Obtaining a DEM
1. Direct extraction of topographic information using well established photogrammetric techniques. This method has evolved from manual interactive collection of breaklines and mass points to a fully automated method, using image matching techniques.
2. Using laser and radar-based sensors to automatically derive elevation information.
Regardless of the method used, the recorded data is post-processed to generate the final DEM.
The DEM is directly used for the generation of numerous products, including Triangular Irregular Networks, ortho-rectification of aerial and satellite imagery, and the production of topographic maps. Geospatial applications include the creation of accurate floodplain maps, terrain models, transportation infrastructure planning and design base maps, and land use management.