Accuracy Assessment Of Measuring Track Geometric State For High Speed Railway With Close-range Photogrammetry

Rail tracks are the important infrastructure facilities that support directly high-speed vehicles running smoothly. The regular geometric state and smooth shape are the key factors that ensure the train running safely. Especially during the period of railway operation, the regularity of track surface is easily affected by the long-term interaction effect between wheel and rail. In addition, possible regional ground deformation may cause roadbed subsidence and track irregularity. So the geometric state of rail track should be periodically measured and checked for the sake of safety.In order to improve the efficiency and accuracy of measuring track regularity for high-speed railway, a new method of close-range photogrammetry is proposed in this thesis. Two photography solutions of track measurement, two-way close-range photogrammetry and moving close-range photogrammetry are presented.Two-way close-range photogrammetry referes to track photographs captured along the rail extending direction. CPIII points are employed as exterior control in the bundle block adjustment processing. Moving close-range photogrammetry captures continuous high resolution digital images of track surface based on moving vehicle to determinate the geometric regularity. The self-calibration bundle block adjustment algorithm is employed to compute the coordinates of track surface with control points set on the rail surface.The determination model of track point coordinate and accuracy assessment method from two-way close-range photogrammetry and moving close-range photogrammetry are respectively proposed. The lens distortion and interior element of digital camera are introduced into the self-calibration bundle adjustment. The simulation experiment is carried out to analyze the photogrametric accuracy and error factors.The simulation testings show that the geometric accuracy of two-way close-range photogrammetry based on the proposed determination model can reach0.1mm and0.6mm respectively in the transverse and vertical rail direction.The moving close-range photogrammery can reach the accuracy of0.2mm and0.3mm respectively in horizontal and vertical direction. The experimental results of the real rail in the JingHu high-speed railway show that two-way close-range photogrammetry can reach the accuracy of2.4mm and1.7mm respectively in the transverse and vertical rail direction. The moving close-range photogrammetric results in the HangYong high-speed railway show the absolute accuracy of track measurement can reach0.6mm and0.8mm, the relative accuracy0.2mm and0.7mm respectively in the rail extending direction and the transverse direction. The proposed close-range photogrammetry method is promising for measuring the geometric regularity with high accuracy and high efficiency in track fine adjustment.