Due to the limit of complex terrain

the structural plane of rock mass is difficult to measure in the geological survey of high and steep slopes. Hence

a new technique is in urgent need to achieve all-around precise measurement. In recent years

the technology of the low-altitude and low-speed small unmanned aerial vehicle (UAV) has been developed rapidly. In this study

three-dimensional (3D) reconstruction of the target was performed using the small UAV with a single-lens reflex camera

based on the patch-based multiview stereo (PMVS) and structure from motion (SfM). By means of field experiments and data post-processing

an application method of the UAV oblique photogrammetry was proposed for the geological survey of the high and steep slope. The preliminary conclusions were also obtained. The valid terrain data was successfully collected by the small multicopter UAV with the single-lens reflex camera. During the process of analysing 3D point clouds

the parameter of the structural surface was extracted by the plane fitting algorithm based on the least square method. The structure plane of rock mass was further drew into the polar-radiation equatorial-plane projection map. Thus

the digital measurement of rock mass in high and steep slope was achieved in this study.