DEM generation from stereo SAR images based on polynomial rectification and height displacement
This work introduces the algorithm on DEM generation from stereo SAR images based on polynomial rectification and height displacement, and experiments according to the algorithm on RADARSAT and airborne SAR images in mountain area. To generate DEM from stereo SAR image, there are three kinds of models mostly to be used: 1) the model of range and Doppler equations, 2) the equivalent line central projection model based on the photogrammetry theory, 3) the parallax and elevation relation model which uses the relation between parallax and elevation to calculate elevation difference and then getting the plane coordinates. The model used in This work can be one of the third ones. In our model, image distortion caused by factors other than elevation is corrected by polynomial rectification, and elevation is decided by the difference of height displacement in the pair of the stereo SAR images. As the first step, a certain elevation, for instance the mean elevation of the image pair, is given to the point in process. Secondly, the height displacement in the left image can be corrected, and then the plane coordinates can be gotten by polynomial rectification functions of the left image. Thirdly, by polynomial rectification functions of the right image, the image coordinates of the "same name point" in the right image are available. Finally, from the difference between the coordinates and the actual ones, a new elevation can be gotten by the model of the height displacement of the right image. These steps can be repeated until the new elevation is very close to the old one. According to the above algorithm, programme has been designed. And then, experiment has been down on RADARSAT image in a mountain area in China (Dali, Yunnan). The accuracy is about 3 pixels. For airborne SAR images, some experiments have been down in another mountain area of China (Zhengzhou, Henan) with 1 meter resolution SAR images, and the results are similar to that of the first experiment. So, the new algorithm on DEM created from SAR image pairs introduced by This work is efficient and practicable. After modification, this method can also be used for mixed pair of SAR and optical images.