Effects of ground-based camera deployment parameters on SfM-Based 3D reconstruction of deformation features on stepped slopes
摘要
Stepped slopes are common in mountainous regions and are characterized by pronounced benches and risers, which generate strong occlusions during ground-based image acquisition and limit the accuracy of Structure-from-Motion (SfM)-based 3D reconstruction of surface deformation features. Despite the increasing application of SfM in slope monitoring, practical guidelines for optimizing ground-based camera deployment on stepped terrains remain limited. To address this gap, this study investigates the effects of ground-based camera deployment parameters on SfM reconstruction accuracy through geometrically scaled physical modeling and field validation. A 1:10 physical model of a rainfall-induced stepped slope was constructed to reproduce representative surface cracking patterns, with rainfall applied solely to induce deformation rather than treated as an experimental variable. Camera height, layout type, inter-camera angular interval, and camera number were systematically varied under controlled single-elevation configurations. Reconstruction accuracy was evaluated using the mean relative error between manually measured and SfM-derived crack widths. The results show that deployment geometry strongly governs reconstruction performance. A camera height of approximately one-third of slope height provides a favorable balance between spatial resolution and coverage. Compared with conventional horizontal layouts, fan-shaped configurations significantly reduce occlusion effects and improve crack-width measurement accuracy. Increasing the number of cameras generally reduces reconstruction error, but the improvement becomes marginal beyond four to five cameras under single-elevation deployment conditions. Under the optimal configuration, the physical model achieved a minimum mean relative error of 4.3%, while the field application at a prototype stepped slope yielded a mean relative error of 12.2%, which is acceptable for routine engineering monitoring. These findings provide practical and cost-effective guidance for ground-based SfM monitoring of deformation on stepped slopes in mountainous terrain.