Urban Extent Extraction Combining Sentinel Data in the Optical and Microwave Range

This paper illustrates a fusion approach to jointly exploit Sentinel-1 (S1) and Sentinel-2 (S2) data to detect urban areas. The proposed procedure is designed to automatically and effectively exploit the specific characteristics of synthetic aperture radar (SAR) and multispectral data, so that it can be safely applied to different urban environments with satisfying results. To this aim, it starts from two previously developed algorithms for urban extent extraction designed for multispectral or SAR spaceborne data. They are first adapted to use S1 and S2 datasets, and then coupled to a novel procedure that merges the two processing chains with the goal to exploit the spectral properties of man-made materials as well as the double bounce backscatter effect that is common in built-up environments. Experimental results in urban areas all around the world show that the proposed approach is successful at combining S1 and S2 information by reducing the errors of the two original techniques.