RAY-BASED DETECTION OF OPENINGS IN URBAN AREAS USING MOBILE LIDAR DATA

The detection of openings like windows or doors is of great interest in the field of urban modeling. Mobile LIDAR data provides valuable 3D information for that purpose. There are generally two main problems: The estimation of wall's surface, and the distinction between opening areas and occluded areas. Indeed, openings may be visible or occluded with regard to the sensor. The method presented in this paper focuses on the detection of visible openings using intersections between laser rays and walls. In particular, it shows that detection of visible openings can be reduced to a single distance threshold once the surface of the wall is computed. Thus all the complexity is actually in the estimation of the wall's surface. The opening contours are then obtained by clustering the visible opening points and fitting them with rectangles. The main advantage of ray-based detection is its robustness to occlusions. This method requires the LIDAR sensor positions and angles for every laser point. Results are evaluated quantitatively on two datasets with ground truth. Qualitative results on larger datasets are also given. The results show good precision. The recall (or completeness) depends on the number of occluded openings.