Assessment of the trueness and precision of smartphone photogrammetry for rock joint roughness measurement

The roughness of rock joint surfaces plays a vital role in the hydrological and mechanical properties of discontinuous rock masses. Applicable and reliable measurements are important for investigating the roughness characterization of rock joints. This research comprehensively evaluates the performance of smartphone photogrammetry for rock joints through a roughness characterization method. Five laboratory-sized rock joint specimens were selected and operated by 24 experimenters to assess the trueness and precision of smartphone photogrammetry based on Structure from Motion- Multi View Stereo (SfM-MVS) photogrammetry technique. Benchmark data from a structure light scanner were used to assess the usability of smartphone photogrammetry through the directional roughness metric method. The results show that it can be applied to achieve acceptable trueness and precision of joint roughness measurements for engraving rock and replica rock joints with no reflective or translucent materials. In addition, the roughness errors of the subsampled models with point intervals of 0.25 mm, 0.5 mm, and 1.0 mm are close to each other.