Generation and Quality Assessment of Stereo-Extracted DSM from GeoEye-1 and WorldView-2 Imagery

Digital surface models (DSMs) extracted from 15 different stereo pairs attained by the combination of GeoEye-1 (GE1) and WorldView-2 (WV2) panchromatic very high resolution (VHR) satellite images are tested. Two of them are pure same-date along-track stereo pairs, one from each VHR satellite, whereas the rest are mixed multidate across-track ones. A quality assessment on the DSMs extracted from the aforementioned stereo pairs, involving both accuracy and completeness, is carried out. Several factors are tested such as sensor model used in the bundle adjustment, number of ground control points (GCPs), radiometric characteristics, satellite imaging geometry, time between acquisition dates, and target land cover. A highly accurate light detection and ranging elevation data is used as ground truth. Overall, 3-D rational functions refined by a zero-order polynomial adjustment by using 7 or 12 GCPs performed slightly better regarding both DSM vertical accuracy and completeness. In relation to the pure stereo pairs, the DSM extracted from the GE1 stereo pair attained better vertical accuracy over the whole study area (90th percentile linear error, LE90, of 2.04 m) but lower completeness (74.50%) than the WV2 one (2.56 m and 83.35%, respectively). The undergoing hypothesis is that the blurrier images from WV2 could have influenced in the improvement of the matching success rate while reducing the vertical accuracy of extracted points. When all the 15 stereo pairs are considered, the vertical accuracy mainly depends on the convergence angle. In addition, the temporal difference between acquisition dates turned out to be the most influential factor regarding completeness values.