High resolution satellite images orthoprojection using dense DEM

According to the recent incoming of high resolution images acquired by the new earth observation satellites (IKONOS, EROS, QUICKBIRD) we are suggested to considered their possible photogrammetric exploitation. The high geometric resolution of such images (up to 0.6 m GSD) and their high radiometric resolution drive us to consider them as possible substitutes of the classic aerial images used for cartographic purposes at the 1:5000/1:2000 scale. In such context we can't omit the heavy incidence of terrain altimetry onto the images georeferencing operations; orthocorrection is necessary to be carried out. This paper, far away from solving the real orthoprojection instances related to the definition of the camera position and attitude, demonstrates as well complex urban DDEM (Dense Digital Elevation Model) completed with volume information of buildings, can improve the planimetric accuracies of the orthocorrected images. A proprietary software, developed by the authors, can automatically extract buildings DEM from a 3D cartography and integrate it with a simple terrain DEM. Results are referred to an orthocorrection carried out by a commercial software. They are certainly conditioned by the out-of-our-control geometric model used by the software itself. The purpose is simply to demonstrate the real improvement of the planimetric positioning obtained using DDEM.