Change detection and deformation analysis using Terrestrial Laser Scanning: Case study of the metro tunnel at Rotterdam central station

A Terrestrial Laser Scanner (TLS) is a powerful tool for surveying. Tens of millions of points are acquired with a high accuracy and within a short time. The resulting point clouds can be used to find changes and deformations. For this project, four point clouds of the metro station and tunnel at Rotterdam central station are available. The processing of the Laser Scanning data can be a time consuming task. Depending on the desired end product, various steps are required. During this graduation project, a method is proposed to find changes and deformation in the repeated TLS point clouds. A key step in this method is to distinguish surfaces in the point clouds that are changed from unchanged surfaces. The unchanged surfaces are investigated in more detail to find deformations in the Signal-to-Noise Ratio. The proposed method consists of three processing steps. The first step is to transform all the scans to the same (absolute) coordinate system. The second step is to divide the point clouds in segments. These segments are planar surfaces in the metro tunnel. During the segmentation matching, corresponding surfaces sampled at two different moments are identified, which is the third step. These matching segments are compared in more details during a deformation analysis. Segments without a match are subject to a change detection. The proposed method is applied to three case studies, using real data from the metro tunnel. The first case demonstrates the use of the method to research the registration accuracy and find occlusions between two scans. The two other cases demonstrate the change detection and deformation analysis. The results are validated using total station and joint meter measurements.GeomaticsEarth Observation and Space SystemsAerospace Engineerin