In this paper, a new criterion based on the Minimum Description Length (MDL) principle is proposed to guide a region growing procedure. Since the MDL principle is known to realize the compromise between complexity of modeling and adequacy to the data in a homogeneous way, it is well suited for detecting cartographic objects in aerial images, because their representation has to be simple and realistic. The procedure is dedicated to segment disparity maps or Digital Evaluation Models into planar regions, and so detect 3D planar patches in the scenes. The principle is shown to be able to introduce constraints on the segmentation. By making one term of the Description Length vary, different levels of representation of the scene are obtained. This makes it possible to get concurrent 3D planar hypotheses. The procedure is applied on disparity maps or on digital elevation models computed on gray level aerial high resolution stereo pairs, in urban context. On these data, those roofs and visible facades are extracted by the procedure.