IN the last ten or more years, with the availability of high-spatial-resolution satellites such as IKONOS, QuickBird,GeoEye, and Resource 3 for the observation of Earth and the
rapid development of some aerial platforms such as airships and unmanned aerial vehicles, there has been an increasing need to analyze high-resolution images for different applications. In
urban areas, surface features are quite complex, with a great variety of objects and shadows formed by elevated objects such as high buildings, bridges, and trees. Although shadows
themselves can be regarded as a type of useful information in 3-D reconstruction, building position recognition, and height estimation [1], [2], they can also interfere with the process-
ing and application of high-resolution remote sensing images