SAR interferometry coherence analysis for snow mapping

Abstract

For climatological and hydrological investigations, the areas covered by snow and their spatial variability are important parameters, particularly in alpine regions. A interferometric SAR technique not only can produce a high-resolution digital elevation models but also can detect the changes in the surface. By comparing four ERS-1/2 repeat pass SAR image in the Tibet Hateau test area, we find that the coherence measurements from the bare soil, bare rock and the short vegetation are significantly high, and lake and snow cover have very low coherence. On other way, the entire target may show very low coherence if there are great decorrelations due to other parameters, such as spatial baseline, rotation and temporal. We will demonstrate the method and result for snow mapping by using both backscattering and coherence measurements with repeat passes ERS-1 image data at the Kunlunshan Mountain, the Tibetan plateau (36°03'N, 91 °00'E). An accuracy of better than 82 % can be achieved if we consider the classification result from TM imagery as the ground truth. The results showed that the coherence measurements provide an effective way to map snow-covered area.