In this paper, our concern was to help understanding the different scatterers responses in an interferometric image of a urban area by studying the different mechanisms that can occur inside the urban canyon. This study relies on a geometric code we specifically developed for this kind of scene. In this example, because of the reflections on the walls, we highlight the impact of the Brewster angle on the interferometric signature. For this reason, we recommend the use of different polarization and incidence angles for urban areas analysis of InSAR image.