Detecting Planar Surfaces in Outdoor Urban Environments

Report No. ARL-TR-4599
Authors: Philip David
Date/Pages: September 2008; 26 pages
Abstract: We describe an approach to automatically detect building facades in images of urban environments. This is an important problem in visionbased navigation, landmark recognition, and surveillance applications. In particular, with the proliferation of GPS- and camera-enabled cell phones, a backup geolocation system is needed when GPS satellite signals are blocked in so-called “urban canyons.” Image line segments are first located, and then the vanishing points of these segments are determined using the RANSAC robust estimation algorithm. Next, the intersections of line segments associated with pairs of vanishing points are used to generate local support for planar facades at different orientations. The plane support points are then clustered using an algorithm that requires no knowledge of the number of clusters or of their spatial proximity. Finally, building facades are identified by fitting vanishing point-aligned quadrilaterals to the clustered support points. Our experiments show good performance in a number of complex urban environments. The main contribution of our approach is its improved performance over existing approaches while placing no constraints on the facades in terms of their number or orientation, and minimal constraints on the length of the detected line segments.
Distribution: Approved for public release
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Last Update / Reviewed: September 1, 2008