Extraction of digital elevation map from parallel-perspective stereo mosaics

In this paper we present an algorithm to extract the Digital Elevation Map or Model (DEM) of a scene from a pair of parallel-perspective stereo mosaics. Stereo mosaics are built from an aerial video of a scene using parallel ray interpolation technique. In addition to the left and right stereo pair, we also build a mosaic along the nadir view to distinguish between the apparent visible and occluded surfaces. This distinction helps us in fitting vertical planes to the occluded surfaces (in nadir view) and developing a complete CAD model of each object (especially buildings in an urban scene). Buildings and trees are two important classes of objects observed in urban scenes. So, the nadir mosaic is segmented and building/tree regions (segments) are identified and separated from terrain. The edges and corners of different surfaces of a building are identified. We match the control points along these edges to their corresponding points in left and right mosaic. Using the disparity between the corresponding points in the mosaics, an elevation map is developed at these points. Optimal surfaces are fit to each of the segments through the edge points. Parts of a DEM of a scene like buildings extracted from a real airborne video are presented in this paper.