In-orbit geometric calibration of multi-linear array optical remote sensing satellites with tie constraints.

When some sub-images lack ground control points (GCPs) or GCPs are not evenly distributed, the estimated camera parameters are often deviated in in-orbit geometric calibration. In this study, a feasible in-orbit geometric calibration method for multi-linear array optical remote sensing satellites with tie constraints is presented. In the presented method, both GCPs and tie points are employed. With the help of tie constraints provided by tie points, all charge coupled devices (CCDs) are logically connected into a complete CCD. The internal camera parameters of all CCDs can then be simultaneously and precisely estimated, even if sufficient evenly distributed GCPs in some sub-images are unavailable. Three GaoFen-6 images and two ZiYuan3-02 images were tested. Compared with the conventional method, the experimental results showed that the deviations of the estimated camera parameters could be effectively eliminated by the presented method. The average geometric stitching accuracy of the adjacent sub-images of all the tested images were improved from approximately 0.5 pixel to 0.1 pixel. The geometric quality of the stitched images was thereby improved.