Stereo image matching using robust estimation and image analysis techniques for DEM generation

Digital Elevation Models (DEM) produced by digital photogrammetry workstations are often used as a component in complex Geographic Information Systems (GIS) modeling. Since the accuracy of GIS databases must be within a specified range for appropriate analysis of the information and subsequent decision making, an accurate DEM is needed. Conventional image matching techniques may be classified as either area-based or feature-based methods. These image matching techniques could not overcome the disparity discontinuities problem and only supply a Digital Surface Model (DSM). This means that matching may not occur on the terrain surface, but on the top of man-made objects such as houses, or on the top of the vegetation. In order to get more accurate DEM from overlapping digital aerial images and satellite images, a 3D terrain reconstruction method using compound techniques is proposed. The area-based image matching method is used to supply dense disparities. Image edge detection and texture analysis techniques are used to find houses and tree areas. Both these parts are robustified in order to avoid outlyers. The final DEM comes from the two parts of image matching and image analysis and hence overcomes errors in the DEM caused by matching on tops of trees or man-made objects