一种隧道点云三维中轴线与横断面提取方法

A Method for Extracting 3D Axis and Cross-Sections of Tunnel Point Cloud

针对采用水平二维中线进行大纵坡隧道横断面提取时误差较大的问题,提出一种高效的隧道点云三维中轴线与横断面提取方法。首先采用边界格网和角度双重约束,提取隧道二维边界点;然后对边界点进行多条件约束的迭代最小二乘拟合,提取水平中线点和侧面中线点,进而将侧面中线点正射投影至水平中线点所在的竖直曲面,得到三维中轴点;最后引入微元思想确定三维中轴点对应的法平面方程,将法平面两侧一定厚度的点云投影至该平面,实现隧道横断面提取。结果表明,该方法能够准确提取隧道三维中轴线和横断面,横断面提取误差在3.06%以内,适用于各种纵坡的直线型、弯曲型隧道。

To address the issue of large error when using horizontal 2D midline to extract the crosssections of large longitudinal slope tunnel,an effective method for extracting the 3D axis and crosssections of the tunnel is proposed.First,the 2D boundary points of the tunnel are extracted using boundary grid and angle constraints.Then,the boundary points are fitted using iterative least squares with multiconditional constraints to extract horizontal and lateral midline points.Next,the lateral midline points are orthographically projected on the vertical curved surface containing the horizontal midline to obtain the 3D axis points.Finally,the infinitesimal method is used to calculate the normal plane equation corresponding to the 3D axis points and a point cloud with a certain thickness on both sides of the normal plane is projected onto this plane to extract tunnel crosssections.The experimental results show that the proposed method can extract the 3D axis and crosssections of the tunnel point cloud with high accuracy.Furthermore,the crosssections extraction error is less than 3.06%;thus,the proposed method is applicable for straight and curved tunnels with varying longitudinal slopes.