Evaluating UAV-Based Quarry Volume Calculations: The Impact of GCP Damage and the Feasibility of Natural Landmarks as an Alternative
Accurate measurement of volume is essential to successful monitoring of quarries and resource management. Existence of stable ground control points (GCPs) ensures aerial surveys to remain precise. However, in quarries, such as in the clay quarry in Ataqa, Suez, Egypt, quarrying activities destroy these points, where volume estimation is challenging. This study investigates the impact of GCP destruction during quarry activities and explores the use of UAV-based photogrammetry supported by natural landmarks (NLMs) as an alternative georeferencing method in the absence of GCPs. While the photogrammetric workflow remained consistent, the key difference lay in the georeferencing stage—using GCPs in the first two steps and exclusively depending on NLMs in the final step. To carry out the study, a three-step process was followed: first, a baseline survey was done using four GCPs; second, the same survey was repeated after quarry operations, still using the four original GCPs; and third, a final survey was performed without using any GCPs—relying only on eight NLMs for positioning—to simulate a situation where the GCPs had been lost or destroyed. In addition, the current research found that volume calculated using NLMs shows approximately 2% difference from the reference volume, which validates their efficiency in ensuring measurement precision without GCPs.