Review of Photogrammetry-Based Techniques for Characterization and Hazard Assessment of Rock Faces

Photogrammetry-based techniques offer a fast and inexpensive way to obtain data needed for geotechnical characterization and hazard assessment of steep rock faces. These techniques also mitigate fieldwork risks associated with conventional structural mapping methods. A camera can function as an accurate survey tool, in most cases as accurate as conventional laser-based survey equipment. Millions of 3D coordinates can be determined from only a few photographs. Mounting a camera on an Unmanned Aerial Vehicle (UAV) solves many of the challenges associated with measuring and mapping steep rock faces. Small low-cost UAVs offer operational flexibility and high quality images. With good photographs taken from appropriate locations, photogrammetry or structure from motion software can generate accurate point clouds, digital surface or terrain models, and orthophotos. With further analysis and interpretation, these can yield the geotechnical data needed to create realistic models in discrete element or finite element software to perform stability assessment.