Research on optimal takeoff positions of UAV integrated GNSS - RTK in producing large scale topological maps for open - pit mines

Abstract

Unmanned aerial vehicles (UAV) are widely used for establishing large scale topological maps. Recently, drones have been integrated with high-quality GNSS receivers which allows real time kinematic positioning (RTK), so are called UAV/RTK. This technology is beneficial to surveyors as they do not need to establish many ground control points in mapping such a complex terrain as open-pit mines. DJI Phantom 4 RTK (P4K) is a UAV/RTK which is of much interest due to its small size and low cost. For open-pit mines, the takeoff position of P4K needs to be seriously considered because of its influence on the accuracy of the digital surface model (DSM) and safety of survey flights. This article presents the method of determining the optimal takeoff positions for UAV in large scale mapping for open pit mines. To evaluate this method, a site of steep and rugged terrain with an area of 80 hectares at the Coc Sau coal mine was chosen as the study area. The results indicate that two optimal locations with altitudes of +50 m and +160 m could be used for taking off the P4K. The accuracy of DSM generated from UAV images using the optimal positions satisfied the accuracy requirement of large scale topological maps at the deepest area of the mine (the altitude of -60 m).