ASSESSMENT OF THE IMPACT OF GROUND CONTROL POINT REDUCTION ON THE ACCURACY OF HIGH-RESOLUTION UAV-PPK PRODUCTS
Ovidiu-Gabriel POP1, Vasile DOHOTAR1 , Dan VELE1
1 Babeș-Bolyai University Cluj-Napoca, Faculty of Geography, 5-7 Clinicilor Street, Cluj-Napoca, Romania, e-mails: ovidiu.gabriel.pop@stud.ubbcluj.ro, vasile.dohotar@ubbcluj.ro, dan.vele@ubbcluj.ro
ABSTRACT. – Assessment of the Impact of Ground Control Point Reduction on the Accuracy of High-Resolution UAV-PPK Products. This study evaluates the impact of reducing the number of ground control points (GCPs) on the accuracy of photogrammetric products within a high-resolution UAV-PPK workflow. The experiment was conducted under controlled conditions, using the same study area, imagery, GNSS infrastructure, and processing workflow. Four scenarios were analyzed. Image coordinates were post-processed in TopoSetter, while photogrammetric processing was performed in Pix4Dmapper. The resulting products include dense point clouds, digital surface models (DSM), and orthomosaics, with an average ground sampling distance of 1.32 cm/pixel. The results indicate a limited increase in horizontal RMSE with decreasing
GCPs (RMSE XY: 0.025–0.030 m) and a higher sensitivity of vertical RMSE (RMSE Z: 0.026–0.060 m), while remaining within acceptable limits for highresolution mapping applications. These findings suggest that reducing the number of GCPs does not lead to a significant degradation of geometric accuracy within the analyzed UAV-PPK workflow.
Keywords: UAV-PPK, photogrammetry, ground control points, horizontal accuracy, vertical accuracy.