Abstract: In response to the problems of low accuracy, long time consumption, and complex data processing existing in traditional bridge alignment measurement technologies, this paper utilizes vehicle-borne 3D laser scanning technology to achieve rapid measurement of bridge alignments.Firstly, the Alpha3D vehicle-borne 3D laser measurement system is used to conduct multi-round dynamic data collection for a large cross-river bridge.Then, methods such as KNN filtering and cloth filtering are employed to eliminate the interference of dynamic vehicles on the bridge deck with the ground point cloud data, so as to extract the ground point cloud.Finally, the measurement accuracy is verified based on the measured data.The experimental results show that the internal consistency mean error of the vertical alignment measurement results in the stable approach bridge area can reach within 5 mm, and the mean error in the cross-river section is approximately 9 mm.Moreover, the multiple measurement results of the cross-river section can reflect obvious vertical dynamic characteristics of the bridge.It can be seen that the method in this paper has the advantages of high efficiency, high accuracy, and simple operation, showing good popularization and application prospects in the daily operation and maintenance detection of large bridges.

Key words: vehicle-mounted 3D laser, bridge alignment, laser point cloud, cloth simulation filtering, dynamic monitoring