In radar remote sensing, classification of urban areas using SAR images is based on the following assumption: there is a dominant scattering mechanism, that is a dihedral-type mechanism. This assumption, widely accepted in the community, is clearly justified by the geometry of urban areas. However, it is noted that most of the results rely on this reference object, that is the perfectly oriented and metallic dihedral. We present here, from an electromagnetic point of view, what happens when the dihedral is disoriented and then we propose a compensation of this effect.