Photogrammetric point determination and DEM generation using MOMS-2P/PRIRODA imagery

This paper describes the process of photogrammetric point determination by bundle adjustment using three-line imagery collected by MOMS-2P, the German Modular Optoelectronic Multispectral Stereoscanner. Since May 1996 MOMS-2P is attached to the remote sensing module PRIRODA of the Russian space station MIR. Its stereo module with three differently oriented lenses allows for the acquisition of three-fold along track stereoscopie imagery. The forward and aft looking channels provide 18 m, the nadir looking high resolution (HR) channel 6 m ground pixel size. For the photogrammetric evaluation 9 image scenes of orbit T083C were composed to an approximately 415 km long image strip covering parts of Southern Germany and Austria. For the German part control points provided by AMilGeo (Amt für Militärisches Geowesen) were used as ground control, with an accuracy of 1.5 m in X,Y and Z. The navigation data are recorded simultaneously with the image lines by the MOMS-NAV package mounted next to MOMS-2P on the PRIRODA module. The orbit positions are expected to have 5 m absolute and 3 m relative accuracy. The INS data have a relative accuracy of 15´. Since MOMS was mounted in orbit during an extra vehicular activity (EVA), there is no precise absolute pointing knowledge of the MOMS camera axes. According to experiences of earlier MOMS data evaluations the camera geometry is simultaneously estimated by self calibration methods. Using small subsets of 12, 7 and 4 control points empirical accuracies of approximately 8 m in planimetry and 10 m in height are achieved, verified by 141 independent check points. Finally a digital elevation model is produced for the entire area (about 50 km x 100 km), which is imaged by all three stereo channels. For that purpose about 700.000 points are transformed into object space using the estimated interior and exterior orientation of the bundle adjustment. The comparison with a reference digital terrain model of AMilGeo results in normaly distributed height differences with a root-mean-square value(rms) also of 10 m (8 m in selected open areas), demonstrating that the achieved accuracy of point determination is valid for the entire area. In the difference DEM (MOMS-AMilGeo) systematic undulations were detected, obviously caused by existing insufficiencies in the attitude model. With a correct model / m (5 m) height accuracies would be possible. Ongoing work is described in (Kornus ea al., 1999)