A UAV-based crack inspection system for concrete bridge monitoring

Crack inspection is one of the most important tasks for concrete bridge monitoring. Traditionally, human-based inspection systems using people's eyes are unsafe and costly. To overcome this problem, a novel unmanned aerial vehicle (UAV) based inspection system is developed to detect cracks on the lateral sides and underside of bridges. Applying obstacle avoidance modules, UAV can reach bridges' lateral sides and underside within a safe distance. Thus the onboard camera can capture images of bridge surface in a high resolution. To locate the positions of cracks and solve the problem of limited horizon of single image, a fast feature-based stitching algorithm is developed. Then an edge detection method using structured forests is utilized to detect cracks on the large panorama. With image distortion corrected, the positions of cracks can be located on the large panorama. Experimental results validate the applicability and efficiency of the proposed UAV-based crack inspection system.