Application and Challenges of Photogrammetry in Underwater Excavations: Case Studies from the Jeju Sinchang-ri and Gunsan Seonyudo Sites, Korea

Abstract. Photogrammetry has become a widely adopted method in underwater archaeology worldwide and is increasingly used in Korean land-based archaeological investigations. However, its application in Korean underwater sites has been challenging due to strong currents and low visibility. This study examines photogrammetric applications in two Korean underwater sites: Jeju Sinchang-ri, where relatively clear visibility allowed for the creation of detailed site maps, and Gunsan Seonyudo, where sedimentation and low visibility required experimental approaches.

At Sinchang-ri, a photogrammetric survey was conducted with a Double Grid method and 10-meter grid units, enabling the production of plan before and after dredging and an artifact distribution map. High-resolution data was acquired using Metashape, resulting in 3D models and orthophotos that effectively visualized site distribution. In contrast, at Seonyudo, the presence of 1-meter-thick sediment made high-resolution artifact mapping difficult. To address this, experimental approaches were tested, including adjusting survey timing based on tidal changes and using underwater lighting for stratigraphic recording. This resulted in the creation of plan of trenches and stratigraphic cross-sections, distinguishing artifact-bearing layers from non-artifact-bearing ones. These case studies highlight the need to refine photogrammetric techniques to suit different underwater environments. As more shipwrecks are discovered, the advancement of photogrammetric methodologies will contribute to more effective underwater surveys and documentation.