Research on tunnel complete profile measurement based on digital photogrammetric technology

Regular measurement of tunnel complete profile is important to the train operation safety. An onboard tunnel clearance measurement device is designed by integrating photogrammetry with linear laser scanning in this paper. The main principle of design is based on the triangulation method using lasers and cameras. Multiple high speed industrial cameras are used to shoot the laser strip profile with a resolution of 1024×1280 pixels per frame. In order to improve the processing performance of the system, Field Programmable Gate Array (FPGA) has been employed as hardware design platform which has a strong ability on dealing with a large amount of image data. The algorithm proposed in this paper is embedded in FPGA hardware completely to process image sequences of 300 frames per second. The overall scheme, FPGA hardware implementation and the results of validation are presented. The results of experiments illustrate a good performance of the proposed system and adaptable ability to the various common tunnel conditions.