Research On Tunnel Light Conditions Luminance Detection Method Based On Point Cloud

This thesis proposes a tunnel luminance measurement method based on threedimensional(3D)laser point cloud intensity,aimed at the low efficiency of current tunnel luminance detection and the problem that related measuring instruments cannot simultaneously meet accuracy and efficiency requirements.The thesis conducted experiments on point cloud intensity correction for tunnel road asphalt,cement materials,and inner wall materials,measuring the bidirectional reflection distribution of tunnel road and sidewall materials,and studied the relationship between point cloud intensity and object reflectance.A luminance calculation model based on point cloud intensity was established,and experiments were carried out in both reduced-scale models and actual tunnels to verify the effectiveness of the 3D laser point cloud technology-based tunnel luminance measurement method.The main research contents and achievements of this paper are as follows:(1)Analysis of the characteristics of the tunnel light environment and the working calculation principles of commonly used luminance meters,and analysis of the impact parameters of optical luminance models.Several optical models’ applicable conditions were summarized,the system composition,working principle,and point cloud data processing method of 3D laser scanners were introduced.Multiple on-site experiments were designed to collect point cloud intensity data under different influencing parameters.(2)The relationship between point cloud intensity and distance,angle,and other parameters was clarified.The functions of point cloud intensity and angle and distance were fitted through experiments on cement,asphalt,and high diffuse reflectivity sidewall materials’ point cloud intensity and bidirectional reflection distribution measurement experiments.A sample database of point cloud intensity-reflectivity for the three tunnel materials was established.(3)A calculation model based on point cloud intensity-object reflectivity was constructed,and the correction method of point cloud intensity using the Lambert model and BRDF model was compared and analyzed.A point cloud intensity correction method based on BRDF measurement values was proposed on the basis of existing correction,which showed significant differences between the results of the two correction models.The results of the BRDF model correction can better describe the object surface reflection characteristics.(4)An automatic tunnel luminance measurement method based on 3D laser scanning was proposed.A method for automatically setting luminance measurement points according to the luminance measurement requirements in the specification was designed from three aspects: measurement point selection,measurement area division,and measurement point layout.The method was validated in an actual tunnel,and the luminance calculation method based on point cloud data was compared with the luminance meter’s measurement results.The calculation error was around 10%,and the efficiency of luminance measurement was significantly improved compared to manual measurement.