Preprocessing Of Space-borne SAR Image In Mountain Area And Building Of Software Platform

Earth observation ability of Space-borne synthetic aperture radar is all weather and around the clock, which is an important application in monitoring and predication of nature disasters in mountain area. But the interference of speckle noise and the geometric distortion phenomenon caused by terrain greatly reduced the application of SAR image in this area. In this paper, the research works on the space-borne SAR image preprocessing for the both problem, including the following contenst:First, mechanism and the statistical characteristics of speckle are described, based on the all developed speckle model. Specifically, three kinds of speckle reducing algorithms are discussed, namely multilook processing, LEE filter and GAMMA MAP filter. These filtering algorithms are respectively applied to TerraSAR-X data in the playground scene and mountain scene. The results are compared and analyzed based on the evaluation criteria, and show that: these filtering algorithms have good inhibitory effects on speckle on SAR image. GAMMA-MAP algorithm is better at maintaining structure on SAR image.Secondly, the principle of geometric distortion on space-borne SAR image in the mountain area is analyzed, and two kinds of geometric correcting methods are introduced: polynomial correcting method and collinear correcting method. Based on the SAR imaging geometry, the paper is focusing on the Range Dopple model. On the basis of this model, we analysed simulated SAR image and terrain correction method. We choosed the experiment area in the town of yingxiu, and the test data include TerraSAR-X SSC data, SRTM DEM of 90 m and airborne DEM of 25 m. Results show that: the resolution of DEM is the key factor of SAR image simulation, and the scattering model has little on the impact; the fractal interpolation of DEM data need to pay attention to whether it will introduce error information; texture feature of simulated SAR image and real SAR image are very consistent. Terrain correction results show that the method is good to eliminate geometric distortion and restore the mountain features.Finally, the SAR image preprocessing method is realized through the programme. A space-borne SAR image preprocessing software platform is built by using IDL programme language. Partialy function modules and interface of the software platform has been demonstrated.