Dense Matching in High Resolution Oblique Airborne Images

An increasing number of airborne image acquisition systems being equipped with multiple smallor medium size frame cameras are operational. The cameras normally cover different viewing directions. In contrast to vertical images, those oblique images have some specific properties, like a significantly varying image scale, and more occlusion through high raising objects, like buildings. However, the faces of buildings and other vertically extended objects are well visible and this is why oblique images are used for instance for visualization purposes. This paper shows results from applying the sophisticated Semi-Global-Matching technique to a set of oblique airborne images. The images were acquired by two systems, namely FLI-MAP 400 (Fugro Aerial Mapping B.V.) and Pictometry (BLOM Aerofilms) over the same area. After the joint adjustment of the images, dense matching and forward ray intersection was performed in several image combinations. The disparity maps were evaluated through the comparison with a reference map derived from LIDAR which was acquired in parallel with the FLI-MAP system. Moreover, the 3D point clouds were analyzed visually and also compared to the reference point cloud. Around 60 to 70 percent of all matches were within a range of ± 3pix to the reference. Since the images were acquired in different flight configurations, the impact of different intersection angles and baselines to the triangulation is quite obvious. In general, the overall structures on the building faces are well represented, but the noise reduction needs further attention.