Positional Accuracy Assessment of Unmanned Aerial Vehicle Photogrammetry in Open-Pit Mines without Ground Control Points Using Coordinate Transformation

Abstract

The popularity of unmanned aerial vehicle (UAV) photogrammetry surveys has increased due to their affordability and the ability to conduct automated flight surveys while simultaneously processing collected data. However, achieving accurate surveying results typically requires the use of dual-frequency Global Navigation Satellite System (GNSS) observations, which can be costly when implemented using multi-frequency GNSS receivers in conjunction with relative positioning methods for UAV and ground control point (GCP) positioning. Hence, more affordable alternatives are necessary to cater to general users. Nevertheless, UAV photogrammetry surveys offer numerous applications suitable for operations with varying required accuracy levels. This study assessed the position accuracy of UAV photogrammetry surveys in open-pit mines without GCPs. As the positioning of UAVs and check points use different methods, coordinate conversion is necessary to test position accuracy accurately. The test revealed a horizontal accuracy of 0.144 m RMSEr and a vertical accuracy of 0.470 m RMSEz, with a 95% confidence level indicating a horizontal accuracy within 0.230 m and a vertical accuracy within 0.913 m. Hence, the acquired horizontal data may be effectively utilized for standard mapping purposes at a scale smaller than 1:400 and adheres to established mapping and Geographic Information System (GIS) standards. Furthermore, the vertical accuracy of the data is suitable for contour interval mapping with a resolution of 1.400 meters or higher.