The model obtained by correlating the pixels in the images or by the laser scanning technique, reproduces with increased fidelity the shape of the elements in the field, in absolute coordinates.

The Digital Terrain Model describes the shape of the terrain and is used to: determine the drainage lines on the slopes, monitor landslides, generate contours, make topographic profiles, make flood risk maps, etc.

The Digital Surface Model is the numerical model of reflectance surfaces. Unlike the digital model of the land, the surface is used in built-up areas, where the land is covered with anthropogenic and natural details. It is used to: determine the height of constructions, perform flood simulations, orthorectification of the orthophotomosaic, etc.