Self-Calibration Adjustment of CBERS-02B Long-Strip Imagery

Due to hardware limitations, such as the poor accuracy of its onboard Global Positioning System receiver and star tracks, the direct georeferencing accuracy of the China and Brazil Earth Resource Satellite 02B (CBERS-02B) by its onboard position and attitude measurements is less than 1000 m at times. Thus, the image data cannot be directly used in surveying applications. This paper presents a self-calibration bundle adjustment strategy to improve the georeferencing accuracy of the onboard high-resolution camera (HRC). An adequate number of automatically matched ground control points (GCPs) are used to perform the bundle adjustment. Both the systematic error compensation model and the orientation image model along with the interior self-calibration parameters are used in the bundle adjustment to eliminate the systematic errors. A self-calibration strategy is used to compensate for the time delay and integrated charge-coupled device translation and rotation errors by introducing a total of ten interior orientation parameters. The preliminary results show that the accuracy of self-calibration bundle adjustment is two pixels better than that of bundle adjustment without self-calibration, and the planimetric accuracy of the check points is about 10 m. The unusual variations of the exterior orientation parameters in some cases are eliminated after enlarging the orientation image intervals and increasing the weights of the onboard position and attitude observations.

I. Introduction

THE resolution of satellite imagery has been largely improved to 1 m or better in recent years. For example, the ground sample distances (GSDs) of IKONOS [1] and QuickBird [2], [28] at nadir have been reported to be 1.0 and 0.61 m, respectively; WorldView-2 [3], [29] has a GSD of 0.46 m (resampled to 0.5 m as required by the government of the United States) at nadir; and GeoEye-1 [4] has a GSD of 0.41 m (resampled to 0.5 m for the same reason above), which is currently the highest resolution among all commercial satellites in the world. All of the above satellites adopted the linear pushbroom imaging mode to acquire high-quality linear-array imagery while integrated with high-accuracy Global Positioning System (GPS) receivers and star trackers to measure its instantaneous position and attitude data at the imaging time. These auxiliary data are transferred to a ground station and are used to perform direct georeferencing. The accuracy of direct georeferencing can achieve 3 m using the auxiliary data of GeoEye-1 [4].