LEVERAGING SMARTPHONE LiDAR TO GENERATE ORTHOMOSAICS: CAN IT REPLACE PHOTOGRAMMETRY?

Photogrammetry is commonly used in the Quaternary geosciences to document natural and excavated fault exposures for paleoseismic applications. The state-of-practice photogrammetric software, such as Agisoft, produces a point cloud from overlapping still images using pixel matching, structure-from-motion, and a proprietary algorithm to mesh images onto the point cloud, resulting in a three-dimensional model. Photogrammetric-based workflows produce high quality orthomosaics but the workflows can be complex, costly, time-consuming, and difficult to apply in remote field locations. The increased prevalence of LiDAR-equipped smartphones and low cost or free image meshing applications offer a potentially convenient alternative to Agisoft and could be seamlessly introduced into existing workflows. Smartphone applications that utilize LiDAR to produce three-dimensional images appear capable of generating similar quality models as Agisoft but at a fraction of the time. Herein, we present an optimized workflow that applies smartphone LiDAR to paleoseismic trench logging and compares it directly to standard Agisoft-based methodologies. This study evaluates these two data acquisition methods based on a standardized criteria which considers field collection efficiency, workflow complexity, three-dimensional model and orthomosaic quality, cost, workflow flexibility, and other factors.