Geometric Quality Improvement and Verification of ZY3-02 Imagery

As the second satellite of the ZiYuan3 series, ZiYuan3-02 (ZY3-02) has been launched successfully in middle of 2016. Compared to the former satellite of ZY3-01, the ZY3-02 has improved its ground sample distance. In order to improve and assess the geo-positioning accuracy of ZY3-02, in this paper, we conducted the on-orbit geometric calibration and accuracy verification work. First, the errors source affecting the imaging model geo-positioning were analyzed, and then a calibration method based on look angle model and compensation matrix were introduced to eliminate the internal and external distortion as well as to improve the geolocation accuracy. Second, the virtual CCD model based on the calibration parameters was established to produce the seamless sensor corrected (SC) image. Finally, large numbers of SC images were selected to verify the geometric quality, including the calibration accuracy, geopositioning accuracy and stereo mapping ability. Experiment results shown that the positioning accuracy improved greatly after geometric calibration with being 1 pixel, and the accuracy of non-calibration images also reached to about 3 pixels which indicated the effectiveness of this calibration model. The elevation and plane accuracy in the stereo mapping experiments archived 3m and 2.5m with only few ground control points (GCPs). All these results demonstrated that the geometric quality of ZY3-02 reached a high level and could meet the requirements of 1:50,000 scale stereo mapping in China. However, as the changing imaging situation and inevitable random noise in the attitude and orbit measurement, the geo-positioning accuracy in fact fluctuated and suffered from the imaging time and imaging area, shortening the calibration period we found could effectively improve the geo-positioning accuracy.