A Comparison of Accuracy of UAS Photogrammetry in Different Terrain Sites

Unmanned aerial systems (UASs) are now standard tools for 3D mapping across diverse terrains. Despite their ubiquity, achieving consistent and reliable mapping results across varied terrains remains a challenge due to differing site conditions. To ensure consistency and the highest accuracy across terrains, it is crucial to discern the optimal flight configuration (defined as the UAS's predetermined flight pattern and altitude to capture overlapping survey images). This paper delves into four distinct terrains: construction, pit, preconstruction, and rock surface sites, collecting photogrammetry data from varied flight configurations. The research revealed that all sites achieved Class A horizontal accuracy, with the best accuracy levels falling within 1−3 times the Ground Sampling Distance (GSD). The findings of this study offer valuable insights to surveyors and other professionals by elucidating the level of accuracy achievable for UAV-based photogrammetric surveying across various sites, enabling them to make informed decisions about flight configurations and data collection methods for more precise and efficient surveying results.