Evaluating RTK GNSS-Assisted Close-Range Photogrammetry for Cultural Heritage Applications without GCPs

This study examines the potential of RTK GNSS-integrated close-range photogrammetry for documenting cultural heritage without the need for ground control points (GCPs). The research focuses on evaluating the GEOSTIX-X5 GNSS receiver, which enables direct synchronisation with a camera via the flash hot shoe, providing precise time-stamping of image capture events. The case study was conducted at Tomb 8 of the Tombs of the Kings in Paphos, a UNESCO World Heritage Site, and compares two datasets: a conventional photogrammetric survey from 2022 using GCPs and a 2025 survey employing GNSS-assisted photogrammetry. Both terrestrial and UAV imagery were acquired and processed in Agisoft Metashape, with accuracy assessment performed through cloud-to-cloud comparison in CloudCompare. Results indicate that the GNSS-integrated approach achieved single centimetre-level accuracy and no systematic scale errors. The findings demonstrate that RTK GNSS-assisted photogrammetry can significantly reduce fieldwork complexity while maintaining high accuracy, offering a promising alternative for heritage documentation where GCP placement is impractical or undesirable.