Accuracy of stockpile estimates using low-cost sUAS photogrammetry
Omar E. Mora, J. Chen, Paul Stoiber, Zoltán Koppányi, Doug Pluta, Rich Josenhans, Matt Okubo
Abstract
The ability to accurately estimate the amount of stockpile material for construction projects can have a substantial impact on project budgets and schedules as well as public safety. Recent proliferation of small Unmanned Aircraft System (sUAS) platforms has made it possible to estimate these stockpiles using inexpensive aerial imagery and photogrammetry at a fraction of the cost and time compared to traditional methods. This study examines the quality of height and volume estimates from sUAS photogrammetry processed through Agisoft Metashape, Bentley ContextCapture, and PixElement, and compared with Global Navigation Satellite System (GNSS) based surveying and Terrestrial Laser Scanning (TLS) measurements. Measurements made on three co-located stockpiles occupying in total 345 m2 and a volume of 487.11 m3 showed that all three software produced results within 3% of TLS measured height and 2% of TLS volume overall, with greater local variation. Moreover, photogrammetry provided complete coverage while the TLS data had voids due to scanner obstructions. Considering that results could be further improved with refinements in technique, this study joins others in demonstrating that sUAS photogrammetry provides a viable alternative to conventional methods for estimating stockpiles.