Improvement of the spaceborne synthetic aperture radar stereo positioning accuracy without ground control points

Compared with optical remote sensing satellites, the geometric positioning accuracy of synthetic aperture radar (SAR) satellite is not affected by satellite attitude or weather conditions. SAR satellites can achieve relatively high positioning accuracy without ground control points, which is particularly important in global surveying and mapping. However, the stereo positioning accuracy of SAR satellites is mainly affected by the SAR systematic delay and the atmospheric propagation delay of radar signals. An iterative compensation method for the SAR systematic time delay is proposed based on digital elevation model to improve the stereo positioning accuracy of SAR satellites without control points. In addition, to address the non-real-time updates of external reference atmospheric param, an iterative compensation method to estimate the atmospheric propagation delay of radar signals is proposed based on standard atmospheric models. In this study, SAR images from the Gaofen-3 (GF-3) satellite with 5 m resolutions were used as experimental data to verify the effectiveness of our proposed method. Simultaneously, the 2D positioning accuracy was better than 3 m and increased by 42.9%, and the elevation positioning accuracy was better than 3 m and increased by 90.2%.