The Effect of System Calibration on Direct Sensor Orientation

The determination of image orientation parameters of any sensor during data acquisition became possible by combined use of an inertial measurement system (IMU) and GPS. In this integrated system, GPS antenna, IMU and imaging sensor are located different position in airborne carrier. Because of this reason, the displacement vectors between sensors have to be determined. Similarly, axes of the IMU and imaging sensor are not same and a mis-orientation matrix exists between them. System calibration is including both calibration of individual sensor and calibration between sensors. The IMU calibration for drifts and biases and the calibration of imaging sensor for interior orientation parameter are components of sensor calibration. Calibration between sensors contains the determination of a constant displacement vector between sensors and a constant mis-orientation matrix between IMU body frame and imaging sensor frame. The boresight misalignment, the relation between the IMU and the imaging sensor is determined by bundle block adjustment using a calibration flight. The small change of correction of interior orientation and 3 shifts and 3 misalignment angles between IMU and imaging sensor directly affect direct sensor orientation. In this study, the effects of the system calibration on direct sensor orientation is investigated based on data set of the test ‘Integrated Sensor Orientation’ of the European Organization for Experimental Photogrammetric Research. For this, bundle block adjustments have been done with different approach using calibration flights. Using these bundle block adjustments, correction for interior orientation and 3 shifts and 3 misalignment angles between IMU and imaging sensor have been determined. The object coordinates of measured image points have been intersected based on GPS/IMU data improved by the boresight misalignment. For each approach, computed checkpoints coordinates have been compared with given reference coordinates. The effect of system calibration on direct sensor orientation has been analyzed comparing results of different georeferencing results using different system calibration parameters.