A Monitoring Method Integrating Terrestrial Laser Scanning and Unmanned Aerial Vehicles for Different Landslide Deformation Patterns

The three-dimensional deformation monitoring of landslides is very complex due to the uncertainty of movement direction and the difficulty in searching the corresponding points before and after deformation. In this study, a landslide deformation monitoring method based on the integration of terrestrial laser scanning (TLS) and unmanned aerial vehicles (UAVs) is presented. This method can quickly obtain high-precision and large-scale terrain information in the absence of sufficient ground control points (GCPs) and can accurately describe the real movement of landslides. The real-time kinematic (RTK) and post-processed kinematic (PPK) are applied to localize the initial positions of TLS and UAV, respectively. The iterative closest point algorithm is applied to register the TLS and UAV point cloud data. Then, the RTK-based GCPs and TLS-based GCPs are obtained to improve the accuracy of UAV data. After that, 3D deformation analyses based on shortest distance method and horizontal deformation based on the difference of orthophotos are applied through point clouds and orthophotos. The proposed method is demonstrated by monitoring a reactivated ancient landslide (Aniangzhai) in Danba County, Southwest China. The real deformation of the landslide has been validated with the registered TLS data. The results indicate that the downcutting of the riverbed and erosion to the slope toe caused by the dam break flood are the main reasons for the reactivation.