Entwicklung und Validierung eines Gesamtsystems zur Verkehrserfassung basierend auf Luftbildsequenzen

Kurzfassung

This dissertation should make a contribution to the further development of airborne traffic detection. The used hardware is an airborne camera system combined with an inertial measurement unit for orientation determination. Mainly computer vision algorithms are presented, which are applied afterwards the image acquisition up to the determination of the most important traffic data. After a short presentation of the used hardware the calibration of the camera’s alignment angles during test flights is explained and its accuracy is analyzed. It is shown that the orientation data doesn’t reach the specified accuracy, which is fortunately less important for traffic detection. After the image preparation, which contains the ortho image generation as well as the clipping of traffic areas, a two-stage vehicle detection algorithm is implemented, which at first rapidly creates hypotheses based on edge filters. In the second stage those hypotheses are verified by a Support Vector Machine which rejects most of the False Posititves. At good conditions the detection reaches completeness rates of up to 90 percent with a low contingent of FP detections. Subsequently a tracking algorithm based on singular value decomposition is applied to associate vehicle hypotheses in adjacent images and determine the average speed. The achieved velocities differ less than ten kph from the manually obtained data. Concluding an alternative orientation method is presented, that automatically determines the airplane’s attitude based on GPS and image information. This is realized by extraction and matching of street segments and additional tracking of ground control points. The results have accuracies of around 0.1 to 0.2 degrees. The innovation of this thesis refers to the combination of rapid pre-selection and more reliable verification of object hypotheses. additionally the automatic extraction of streets as landmarks for orientation determination and its fusion with relative orientation parameters as stabilization are novel.