ABSTRACT
One of the key instruments for mapping large areas of impervious surfaces is satellite remote sensing. However, accurate mapping of impervious surfaces remains a challenging task due to their diversity and the diversity of urban land covers, and thus impervious surfaces are often easily confused with other land cover types in terms of spectral signatures. For instance, bright impervious surfaces are often mixed with dry soils and sands, while dark impervious surfaces tend to be confused with shade and water. In order to reduce the spectral confusion, synthetic aperture radar (SAR) has been widely reported to provide complementary information. SAR works in all weather and time conditions, and thus is free from the influence of cloud occurrence. Moreover, existing research shows that SAR is very sensitive to ground surface roughness, shape, structure, and dielectric properties of illuminated ground targets, and thus can provide complementary information to optical data (Henderson and Xia 1997). Therefore, these characteristics and information should be of great benefit to separate different ground targets when their spectral signatures are similar in the visible and near-infrared wavelength range, as with bright impervious surfaces and dry soils/sands, or dark impervious surfaces and shade/water.
