Traffic Sign Occlusion Detection Using Mobile Laser Scanning Point Clouds

For survey and maintenance of traffic signs, this paper presents a novel traffic sign occlusion detection method using 3-D point clouds and trajectory data acquired by a mobile laser scanning system. To produce a maintenance guide, our method aims to obtain the degree of occlusion by analyzing the spatial relationship between traffic signs, surroundings, and drivers on the road. First, a detection method considering both reflectance and geometric features is developed to capture traffic signs. Next, to simulate the driver's view, a trajectory-based method is proposed to determine driver's observation location and the corresponding observed traffic sign. Finally, to determine whether a traffic sign is in occlusion, a hidden point removal algorithm is adopted and carried out. Furthermore, we develop two indices to evaluate the degree of occlusion. The proposed method is tested using two point cloud data sets collected by an RIEGL VMX-450 system along a 23.68-km-long urban road. The obtained results illustrate the feasibility of the proposed occlusion detection method.