Analyzing a block of HRSC image strips for a simultaneous bundle adjustment

Abstract

10 years ago the first European interplanetary mission Mars Express was launched and sent into orbit around Mars. One of the scientific instruments on board the orbiter is the High Resolution Stereo Camera (HRSC). This multi-line sensor with five panchromatic and four multispectral CCD lines was developed by the German Aerospace Center (DLR) for photogrammetric mapping purposes. It images the Martian surface with a resolution of up to 12 m per pixel, depending on the altitude. The along-track stereo capability of the camera delivers image strips with three-dimensional information, which cover nearly the whole planet. For a derivation of more accurate digital terrain models and orthoimages the orientation data of the camera is improved via bundle adjustment. To map larger regions overlapping image strips can be used to form photogrammetric blocks, thus allowing a simultaneous adjustment of the different strips. Compared to the adjustment of individual strips, an adjustment of the entire block reduces not only local, but also regional inconsistencies in the data. With the growing number of HRSC image strips in this ongoing mission, number, size and complexity of potential blocks increases. To cope with these data a method for a semi-automated analysis, selection and combination of suitable strips for the design of more accurate and reliable blocks has been developed. The method takes the inhomogeneity of the HRSC data into account by adapting the processing parameters, if necessary for each strip.