Automated and Efficient Method for Extraction of Tunnel Cross Sections Using Terrestrial Laser Scanned Data

An automated and efficient method for extraction of tunnel cross sections using terrestrial laser scanner (TLS) data is presented. In this process, a three-dimensional (3D) point cloud acquired from the TLS is projected onto a horizon plane, converted to a two-dimensional (2D) planar image, and skeletonized to estimate the tunnel centerline. Stations from which cross sections are extracted are estimated from that centerline, which is vectorized and smoothed for better estimation. From those stations, cross-sectional planes are estimated, and point groups surrounding the planes are extracted. By using these point groups, the azimuth angles of the cross-sectional planes are adjusted, and the final cross sections are generated by projecting the nearby points to the adjusted planes. The performance of the proposed method was evaluated by applying it to a real tunnel and comparing the results with those from a conventional method that uses a total station. In the results, the cross sections were extracted at the stations corresponding to the conventional method. The proposed method proved itself to offer advantages, including detailed description and improved surveying and data processing efficiencies.