Comparative Study of UAV Mapping with and without Ground Control Points (GCPs)

Unmanned Aerial Vehicles (UAVs) have transformed geospatial data acquisition, yet the necessity of Ground Control Points (GCPs) for spatial accuracy versus operational efficiency remains a critical topic of investigation. This study presents a comparative analysis of UAV mapping accuracies achieved with and without the integration of GCPs. Conducted at the Asian Institute of Technology (AIT) in Pathum Thani, Thailand, the research utilized a DJI Phantom 4 Pro for aerial imagery and a Javad TRIUMPH-2 GNSS receiver to establish survey-grade GCPs and Check Points (CPs) via Real-Time Kinematic (RTK) methods. Flight parameters included a 90-meter altitude with 70% forward and side overlap, yielding a Ground Sampling Distance (GSD) of 3.45 cm/pixel across a 0.252 km² area. The photogrammetric processing resulted in a Root Mean Square Error (RMSE) of 26.26 cm for GCPs and 76.76 cm for independent CPs. The findings indicate that while orthophotos and Digital Surface Models (DSMs) processed without GCPs exhibit smooth