Multi-Sensor Geometric Documentation of Cultural Heritage at Risk Across Inland, Coastal and Shallow-Water Environments

Abstract

Highlights What are the main findings? Multi-sensor geometric documentation produced site-specific 2D, 2.5D and 3D evidence layers across eight inland, coastal and shallow-water cultural heritage sites. Optical photogrammetry, acoustic sounding and flash LiDAR provided operationally complementary information on exposed remains, unstable terrain, submerged structures and underwater morphology, addressing different spatial scales, targets and environmental conditions. What are the implications of the main findings? Cultural heritage documentation in risk-related contexts should be designed around the conservation question and site conditions, rather than around a single sensor, product type or level of geometric detail. The value of documentation products lies in their ability to transform visible, submerged and terrain-related conditions into measurable spatial records for future assessment and monitoring. Abstract Climate-related and environmental hazards affect cultural heritage sites in markedly different inland, coastal, lacustrine and underwater settings, creating documentation requirements that cannot be addressed by a single sensing approach. This study presents the multi-sensor geometric documentation of eight cultural heritage sites. Unmanned aerial vehicle (UAV) photogrammetry was applied to six inland and coastal sites, while underwater photogrammetry, unmanned surface vehicles (USVs), acoustic sounding and a prototype green-wavelength flash LiDAR were used at three shallow-water sites. The campaigns produced orthomosaics, elevation models, dense point clouds, textured meshes, bathymetric maps and underwater LiDAR point clouds at scales appropriate to the conservation problem of each site. The resulting products document exposed architectural remains, excavation areas, cliffs and unstable slopes, lake-margin changes, submerged masonry, wooden structures and lakebed morphology. Their main contribution is the establishment of spatially explicit, site-specific baselines that provide measurable geometric and visual evidence for condition assessment, future repeat-survey comparisons and the spatial integration of environmental, archaeological and conservation information. The study demonstrates the operational and information complementarity of optical, acoustic and active ranging approaches, which address different documentation scales, environmental constraints and heritage targets, and provide distinct spatial evidence that can serve as potential inputs to subsequent digital twin and decision support applications.