Potential and limits of InSAR data for building reconstruction in built-up areas

The automatic reconstruction of buildings for the generation of city models is of great interest for different tasks. Three-dimensional information can be directly obtained from both, laser (LIDAR) and radar (InSAR) measurements. The features of both sensors are compared. The data acquisition by SAR is described, with emphasis on the special properties of the interferometric SAR principle. A segmentation approach for building reconstruction is proposed. The results show that building reconstruction is possible from InSAR, but the achievable level of detail cannot compete with LIDAR. The main source of limitation is the inherent side-looking scene illumination of SAR, giving rise to disturbing phenomena interfering with often large parts of the scene. Geometric constraints for the location and size of such problem areas are derived. To identify areas of unreliable data in SAR images of a built-up area, corresponding elevation data are analysed. The impact of the phenomena layover, shadow and dominant scattering at building locations is considered. For this task, a hybrid elevation reference is required. The buildings and the surrounding ground are represented as CAD planes. Natural objects like trees and bushes remain in the raster representation.