Calibration Aspects in Direct Georeferencing of Frame Imagery

The determination of the exterior orientation by a combination of an inertial measurement system (IMU) with relative kinematic GPS-positioning – the direct georeferencing has a growing number of applications for standard photogrammetric projects. One mayor problem is the determination of the relation between the camera and the IMU the boresight misalignment. The rigorous mathematical model requires the computation and use of it in an orthogonal coordinate system like a tangential system in relation to the earth ellipsoid. But the final data acquisition usually shall be made directly in the national coordinate system. The procedure to use the boresight misalignment without loss of accuracy in the national coordinate system in any location will be explained. Results of the stability of the misalignment over the time will be shown. If the results of the boresight calibration shall be used for different image scales, also the inner orientation has to be determined together with the boresight misalignment. This has to be done with 2 different flying heights over a calibration site. Another problem is the limited accuracy of the model set up, today the direct sensor orientation is often not accurate enough to guarantee a model set up without a disturbing size of the y-parallaxes. This can be solved with a combined adjustment of the direct sensor orientation together with image coordinates of tie points, but without control points.