Comparison of stereo-extracted DTM from different high-resolution sensors: SPOT-5, EROS-a, IKONOS-II, and QuickBird

Digital elevation models (DEMs) extracted from high-resolution stereo-images (SPOT-5, EROS-A, IKONOS-II, and QuickBird) using a three-dimensional multisensor physical model developed at the Canada Centre for Remote Sensing, Natural Resources Canada were evaluated. In a first step, the photogrammetric bundle adjustment was setup for the stereo-images with few accurate ground control points. In a second step, DEMs were generated using an area-based multiscale image matching method and then compared to 0.2-m accurate light detection and ranging (LIDAR) elevation data. Elevation linear errors with 68% confidence level (LE68) of 6.5, 20, 6.4, and 6.7 m were achieved for SPOT, EROS, IKONOS, and QuickBird, respectively. The poor results for EROS are mainly due to its asynchronous low orbit, which generated large geometric and radiometric differences. However, when such differences were not large, LE68 of 10 m (four pixels) was achieved. Since the SPOT, IKONOS, and QuickBird DEMs were in fact digital surface models, where the height of land covers was included, elevation accuracy was performed only on bare surfaces (soils and lakes), where there was no difference between the stereo-extracted elevations and the LIDAR data. LE68 of 2.2, 1.5, and 1.2 m were then obtained for SPOT, IKONOS, and QuickBird, respectively. When compared to sensor resolution, multidate across-track SPOT with a smaller base-to-height (B/H) ratio of 0.77 achieved three to four times better results than same-date in-track IKONOS and QuickBird with B/H of around 1: 0.5 pixels versus 1.5 or 2 pixels.