Comparison of the Accuracy of Dem from Spot Hrs Two-fold Stereo Data and Hrs/hrg Three-fold Stereo Data in Barcelona Test Site

ISPRS and CNES announced the HRS (High Resolution Stereo) Scientific Assessment Program during the ISPRS Commission I Symposium in Denver in November 2002. 9 test areas throughout the world have been selected for this program. For the Barcelona test site not only two-fold stereo HRS data but also HRG data of the same region have been acquired. This leads to the possibility to compare the DEM production and accuracy differences between two-fold and three-fold stereo data sets. For the derivation of the DEMs, the DLR own stereo processing software, developed for the MOMS-2P three line stereo camera is used. The matching process using three images is more robust than with two images due to the possibility to eliminate blunders by matching three stereo pairs. Furthermore the forward intersection of the three image rays allows better constraints for the object space intersection. Due to these reasons the DEM filtering in object space that is necessary for DEMs from two-fold stereo is very much reduced in the case of three-fold stereo data. The derived DEMs are compared with the high precision reference DEM by several methods regarding: height accuracy, location accuracy, blunders, error budget depending on surface properties etc.,. .