Methods for exploiting the relationship between buildings and their shadows in aerial imagery

This paper describes computational techniques for utilizing the relationship between shadows and man-made structures to aid in the automatic extraction of man-made structures from aerial imagery. Four methods are described that perform the prediction of structure shape, grouping of related structures, verification of individual structures, and structure height estimation. In each method the relationship between structure and cast shadows is exploited in a unique fashion. Key issues involve the accurate localization of the structure/shadow boundary and the shadow edge, and attribution of shadow segments to structure hypotheses. We present several examples that show how each method is used within the task of building detection, delineation, and height estimation.