DTM - is a topographical model of the Earth that is processed by specific software, it has digital terrain elevation. It is represented on a scale between 1:50 and 1:500. Basics for DTM's are break lines representing edges of objects, sides of buildings, all the small changes in height of the relief.

DSM - is crude photogrammetry, 3D representation of the terrain that includes elements such as buildings, vegetation, high voltage lines and the remaining elements and manure containing heights. From its processing will result DTM (Digital Terrain Model).

The difference between DSM and DTM: