PTZ Camera-Based Image Processing for Automatic Crack Size Measurement in Expressways

Cracks in road surfaces are among the most critical problems in the management of expressways. Their sizes, which not only have severe consequences in relation to expressway safety, decide maintenance timing, which if accurately estimated, can prevent the rapid development of crack disease. Currently, the main techniques used for crack size measurement makes use of either human inspection or sophisticated mobile equipment, which are respectively, very time consuming, labour-intensive, and difficult to implement in civil engineering. Thus, there is great interest in practical and highly efficacious automated crack identification systems coupled with low-cost data-processing sensors. A PTZ (pan/tilt/zoom) camera-based image processing idea is investigated in this paper for crack size measurement in expressways in China. The proposed method consists of four steps: 1) image acquisition, 2) corner-based line size calculation, 3) pixel size calculation, and 4) crack size estimation. A case study of roadway lane images and crack images, collected from China G4/Jingshi, is conducted to demonstrate the feasibility of the proposed method. The results demonstrate that PTZ camera-based image processing is capable of efficiently quantifying cracks, obtaining high accuracy crack size results at range of 0 m to 40 m. The method shows promise for crack size measurement in a cost-effective manner and can provide an objective and timely means for transportation agencies to conduct maintenance plans.