Influence of System Calibration on Direct Sensor Orientation

The determination of object coordinates based on direct sensor orientation is an extrapolation from the projection centers to the ground coordinate system. Like any extrapolation, it is sensitive to random and systematic errors, as well as, to improper data handling. Direct sensor orientation is based on the combination of an Inertial Measurement System (IMU) and GPS. The GPS antenna, the IMU, and the imaging sensor are located in different positions, and the latter two have different orientations. Therefore, the calibration of all sensors and the relation between the sensors is of vital importance for precise ground positioning. The system calibration includes the determination of the boresight misalignment, the interior camera orientation, and the GPS antenna offset. A rigorous mathematical model is required. The inner orientation of the camera used has to be determined under flight conditions to achieve sufficient results. In this paper, the influence of the system calibration to the direct sensor orientation and improper data handling will be shown.