High-Resolution UAV-Videogrammetry for Discontinuity Mapping in Steep Rock Slopes

Abstract

Characterizing rock mass discontinuities in steep and complex terrain is a critical challenge in geotechnical engineering. Conventional field surveys are often unsafe and provide limited data, while standard UAV-based photogrammetry can be constrained by fixed flight plans and conclusions. This study presents a UAV-videogrammetry workflow for generating high-resolution, spatially accurate 3D models of rock slopes for detailed discontinuity analysis. By capturing continuous 4K video with a UAV in a dynamic, free-flight mode, we achieve dense surface coverage, even in geometrically complex areas like overhangs and recessed zones. A novel semi-georeferencing technique using coded targets enables precise model alignment in a local coordinate system without requiring GNSS, enhancing field applicability. Comparative analysis demonstrates that this approach yields a 20-fold increase in point cloud density and superior orientation accuracy (RMSE of 2^∘ for dip, 7^∘ for dip direction) compared to conventional methods. The resulting high-fidelity models allow for more complete joint set identification and a more comprehensive kinematic stability assessment, providing a safer, more efficient, and scalable solution for rock slope characterization.