A joint geometric calibration technique for GF-3 SAR image in wide area

In order to obtain the accurate SAR orthophoto over wide area, it is necessary to modify the geometric parameters for each of the SAR images. However, it is time consuming and laborious to correct each of the SAR images over wide area, which seriously decreased the efficiency of SAR image analysis. Therefore, a wide-area joint geometric calibration method is proposed in this paper. Firstly, the independent system-level calibration parameter is calculated using several SAR images on the basis of R-D model. Secondly, the influence of atmospheric delay component is removed from the system-level calibration parameters. Then, the optimal system-level calibration parameters are obtained based on the least squares adjustment principle. Finally, the other SAR images are corrected using the optimal system-level calibration parameters.In this paper, 32 scenes of GF-3 SAR images covering the central and eastern part of China are used for joint geometric calibration. The positioning error of the calibrated SAR images is less than 9 m. The experimental results show that the accuracy of geometric calibration for GF-3 SAR images can be improved by the proposed approach, and thus the effectiveness and feasibility of the proposed approach is demonstrated.