铁路桥梁线形测量对于桥梁健康检测与确保铁路安全运营具有重要作用。为提高运营铁路钢桁拱桥线形测量效率，以某3跨钢桁拱桥为例，运用地面激光扫描（TLS）技术对桥梁杆件进行整体化扫描，从桥梁线形测量精度、扫描完整性、点云个数等3方面，分析出最佳的桥梁扫描测站数为10个。运用3DNDT点云配准算法将各测站一一配准，桥梁点云配准精度为2 mm，将桥梁点云投影至xoy平面，用半径滤波器进行噪声点的去除，得到完整“纯净”的桥梁点云模型。提出点云等距切片与点云平面切片算法提取桥梁线形，并将线形点云数据导出在AutoCAD中拾取坐标。将点云切片法提取的TLS测量值、全站仪法测量结果与原始成桥线形做比较分析，结果表明：在桥面线形分析中，两方法均在跨中处A₅点测量出最大变形，分别为12.69 mm、10.29 mm，两方法的最大相互较差R为2.4 mm，相关系数优于99.93%；在拱轴线线形分析中，点云切片法与全站仪法在主桁上弦跨中B₄点位测量的最大变形为6.2 mm、3.9 mm，在主桁下弦跨中B₁₀点位测量的最大变形为5.9 mm、3.5 mm，两方法的最大互相较差R为3.2 mm，相关系数优于99.87%，验证了点云切片算法的有效性与TLS测量的高精度性。拱轴线横向线形未出现明显侧移，点云等距切片得到的19个吊杆垂直度保持良好，未发生扭转与偏移。该成果对于运营铁路钢桁拱桥的线形分析与点云处理方法可提供相应的思路和参考，具有重要的实用价值。

The alignment measurement of railway bridge plays an important role in bridge health detection and the safe operation of railway. In order to improve the efficiency of alignment measurement of steel truss arch bridge in operation railway, this study constructed a complete “pure” bridge point cloud model. It took a three-span steel truss arch bridge as an example and used the terrestrial laser scanning (TLS) technology to scan the bridge members as a whole. From the three aspects of bridge alignment measurement accuracy, scanning integrity and point cloud number, the optimal number of bridge scanning stations was determined as 10. The 3DNDT point cloud registration algorithm was used to register each station one by one. The accuracy of bridge point cloud registration is 2 mm. The bridge point cloud was projected onto the xoy plane and the noise points were removed by the radius filter. The point cloud equidistant slicing and point cloud plane slicing algorithm were proposed to extract the bridge alignment, and the alignment point cloud data was exported to Auto CAD to pick up the coordinates. The point cloud slicing method was used to extract the TLS measurement value, and the total station method measurement result was compared with the original bridge alignment. In the analysis of the bridge deck alignment, the two methods measured the maximum deformation at the mid-span A₅ point as 12.69 mm and 10.29 mm. The maximum mutual difference R of the two methods is 2.4 mm, and the correlation coefficient is better than 99.93%. In the analysis of arch axis alignment, the maximum deformation of point cloud slicing method and total station method is 6.2 mm and 3.9 mm at B₄ point in the upper chord span of main truss, and 5.9 mm and 3.5 mm at B₁₀ point in the lower chord span of main truss. The maximum mutual difference R of the two methods is 3.2 mm, and the correlation coefficient is better than 99.87%, which verifies the effectiveness of point cloud slicing algorithm and the high precision of TLS measurement. There is no obvious lateral displacement in the transverse alignment of the arch axis. The verticality of the 19 suspenders obtained by the point cloud equidistant slicing remains good, and no torsion and offset occurs. The research results provide a reference for the alignment analysis and point cloud processing methods of the operating railway steel truss arch bridge, and have important practical value.