Rockfall feature investigation and kinematic simulation based on nap-of-the-object photogrammetry and GIS spatial modeling

On-site investigation and numerical simulation are the main methods for assessing the risk of rockfall disasters. Unmanned aerial vehicles (UAVs) have been widely used because they can quickly obtain geospatial data. However, in a complex terrain environment, it is difficult to ensure reliable positioning accuracy and resolution of geospatial data collected or constructed at the same flight altitude. Therefore, it is difficult to complete the detailed investigation of rock mass characteristics, and the reliability of the simulation results of rockfall motion characteristics will also be affected. This article summarizes a new image acquisition method and three-dimensional (3D) modeling ideas. Furthermore, in this study a risk assessment is conducted of a slope where a rockfall disaster has occurred. Through this method, the real-world 3D model with a positioning accuracy of less than 5 cm and digital surface model (DSM) data with sub-centimeter resolution of the research area are obtained. Using these data, the rock mass characteristics and the mechanism of disaster formation are analyzed, and the motion characteristics of potential rockfall are numerically simulated in a geographic information system (GIS). After comparing and analyzing the simulated superior trajectory with the on-site terrain, it is found that the trajectory simulated using high-resolution terrain data can better represent the actual movement of falling rocks. The method and process summarized in this paper can provide technical reference for the investigation and evaluation of the risk of rockfall disasters under complex terrain conditions.