System calibration for direct georeferencing

Within the last years extensive tests were done to investigate the accuracy performance of integrated GPS/inertial systems for direct georeferencing in airborne photogrammetric environments. Based on commercially available high performance GPS/inertial systems direct georeferencing was shown to be a serious alternative to standard indirect image orientation using classical or GPS-supported aerial triangulation. Nonetheless, correct overall system calibration including the GPS/inertial component as well as the imaging sensor itself is the limiting factor in this approach. Since direct georeferencing without ground control relies on an extrapolation process only, remaining errors in the system calibration will significantly decrease the quality of object point determination. Therefore, special focus has to be laid on the overall system calibration procedure. Within this context the stability of system calibration over longer time periods and the influence of additional self-calibration on the calibration parameter estimation are of special interest. The investigations presented in this paper are based on test material from a real flight test, where as one part of a big project a calibration field was flown several times within a two month period using the same GPS/inertial-camera system installation. From this test data first statements on the long term stability of system calibration are feasible, which are important especially from a practical point of view when applying direct georeferencing in photogrammetric production processes. KURZFASSUNG In den letzten Jahren wurden ausgiebige Tests zur Ermittlung des Genauigkeitspotenzials der direkten Georeferenzierung mi