The increasing stereoscopic capabilities of radar acquisition system (ERS, RADARSAT) and optical systems (SPOT) allow automatic generation of digital terrain models, which are images where each pixel corresponds to the height of the point represented.

Pairs of stereoscopic images obtained by consecutive photographs taken during flight over a region are transposed after correction by epipolar geometry . By estimating the disparity between two images, it is possible to evaluate the relative height of each point. The robustness of the process is ensured by modelling and taking into account the geometric nature of the elements observed (here polyhedral buildings).

The knowledge of building heights in an urban environment is very useful for broadcasts, the land register, topography, etc.