Algorithms and Experiment on Sar Image Orthorectification Based on Polynomial Rectification and Height Displacement Correction

This paper introduces the algorithm on SAR image orthorectification based on polynomial rectification and height displacement correction, and experiments according to the algorithm on ERS-2, RADARSAT, and airborne SAR image in mountain area. Many factors result in SAR image distortion, and most of them can be corrected by polynomial rectification. But the distortion of SAR image brought by elevation is very difficult to be corrected by polynomial rectification. In this paper, height displacement caused by elevation is corrected in advance according to the slant distance and elevation of each pixel, and the other distortion is corrected by polynomial rectification. Compared to other orthorectification algorithm on SAR image, it is very easy to implement. According to this method, programme has been designed. And then, experiment has been down on RADARSAT image in a mountain area in China (Dali, Yunnan), and polynomial rectification on the same image also has been down by the same ground control points. The accuracy of the former is about 2.8 pixels, and the latter 44.4 pixels. In this area, the most elevation difference of the ground control points is about 2972 meters. Some other experiments have been down on ERS-2 image (Chengdu, Sichuan), and 3 meters resolution airborne SAR image (Dabieshan, Anhui), and the results are similar to that of the first experiment. So, the new algorithm on SAR image orthorectification introduced in this paper is efficient and practicable for SAR image orthorectification in mountain area.