Integrated geometric self-calibration of stereo cameras onboard the ZiYuan-3 satellite

The geometric quality of images is a principal concern for a stereo mapping satellite. On-orbit geometric calibration (GC) is an essential processing step that is always performed to ensure the geometric accuracy of satellite images. However, the traditional GC method is typically expensive and inefficient due to a large dependence on ground-based locations. Although recent GC methods based on relative constraints between images can substantially reduce plane constraints, which are used as the benchmark measurements in the traditional method, there is a strong correlation between elevation and camera orientation that necessitates additional elevation constraints. This paper proposes an integrated GC method to compensate for systematic errors in the three linear cameras (TLC) of the ZiYuan-3 (ZY-3) satellite. The relative constraints and the stereo intersection constraints from two sets of overlapped TLC imagery pairs allow for the removal of dense plane constraints, as well as elimination of the GC dependencies from the additional elevation constraints. This paper also systematically analyzes the relationship between elevation error and camera GC accuracy, proposes a unified GC model for TLC cameras based on matrix decomposition, and develops a suitable global estimation method for the solution of GC parameters. The method was validated through experiments performed on the TLC images, and satisfactory results indicated that it effectively compensates for systematic errors by onboard stereo TLC cameras.