Geospatial accuracy evaluation of a 3D Gaussian Splatting reconstruction from UAV video with GNSS metadata synchronisation

This study evaluates the geospatial accuracy of 3D Gaussian Splatting for rapid 3D reconstruction from UAV video integrated with GNSS metadata synchronisation. The reconstruction quality was assessed in terms of relative geometric consistency and absolute geospatial accuracy, using a reference model generated through close-range photogrammetry (CRP) as a baseline. The experiment used 54 extracted video frames and nine geospatial checkpoints to evaluate both geometric and geospatial accuracy. Experimental results show that GS achieves millimetre-level structural consistency, with an ICP RMS of 0.0048 m, which is comparable to the photogrammetric reconstruction accuracy reported in similar UAV mapping studies. In terms of absolute positioning, the GS model demonstrates moderate horizontal accuracy (CE90 = 5.26 m) and strong vertical accuracy (LE90 = 0.56 m) when reconstructed directly from video frames enriched with GNSS metadata. Comparative analysis indicates that photogrammetric workflows provide superior absolute geospatial control when Ground Control Points (GCPs) are available. GS enables faster reconstruction and stable geometric representation, supporting rapid mapping applications. However, horizontal positional drift remains a key limitation, mainly caused by temporal misalignment between video frames and GNSS metadata rather than reconstruction instability. With improved synchronisation or external geospatial constraints, GS shows strong potential for UAV-based rapid 3D mapping workflows.