随着激光扫描技术精度和效率的提高, 可获得高精度点云的地面三维激光扫描技术已被广泛应用于地铁隧道变形监测、结构构建等领域。但在测量的隧道数据中, 有很多来自隧道上的附着物的数据须要剔除, 以便对隧道进行变形分析。基于三维激光扫描数据, 以运营中的地铁隧道为研究对象, 提出了一种断面分析方法。针对数据中存在的大量粗差, 提出了以残差1范最小为平差准则的椭圆拟合方法, 利用自适应的阈值剔除粗差。采用分段圆弧代替整体椭圆进行断面分析。对提取的断面进行了形变分析, 实验结果表明, 该方法能够剔除数据中的粗差, 采用分段圆弧分析能准确反映隧道的形变。

With the improvement of the accuracy and efficiency of laser scanning technology, three-dimensional (3D) terrestrial laser scanning (TLS) technology, which can obtain high precise points-cloud, has been applied in the field of deformation monitoring of subway tunnels, structures building and other fields. However, the data contains many outliers, which are produced by pipe and bolt holes and should be removed for deformation analysis. Based on the 3D TLS technology, taking the subway tunnel in operation as the research object, we propose a new cross section analytical method. We use an ellipse fitting method based on 1-norm minimum residual algorithm to deal with the points which are not on the tunnel cross section. An adaptive threshold selection method is introduced to filter the points which are not on the tunnel cross section. Circular arcs model, instead of overall oval model, is adopted to analyze the deformation of subway tunnel. Deformation analysis of the extraction cross section is tested. The results indicate that this method can eliminate gross errors in the data and the cross section method using circular arcs model can more accurately reflect the tunnel deformation.