Three-dimensional topographic mapping with ASTER stereo data in rugged topography

Digital elevation models (DEMs) were generated from a stereo pair using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) backward and nadir images with 27.7/spl deg/ intersection angles (B/H = 0.6) over a high relief area of the Canadian Rocky Mountains. Fifteen ground control points were a good compromise to compute the stereo-bundle adjustment when they are only 25-30 m precise to avoid their error propagation in the modeling. It enabled to keep accuracy on the order of one pixel (15 m). DEM accuracy was then evaluated along the full process and as a function of different parameters. Applying the calibration of charge-coupled devices in order to reduce the striping effects improves the DEM accuracy by a factor of 10%. The major problems in the image matching were the clouds, snow, lakes, and occluded/shadowed areas, which generated mismatched areas and "artificial" relief in the lakes (1000-2000 m) during the correlation process and the automatic interpolation method. Postprocessing the DEM with semiautomatic three-dimensional tools improved its accuracy by a factor of 10%. The final results (LE68 and LE90 of 28 and 51 m, respectively) were obtained with the interactive correction of lake elevations, but without taking into account the large mismatched areas, which were specific to this challenging mountainous study site.