Digital Documentation of the Ain Akrine Archaeological Site (Lebanon): A Hybrid UAV Photogrammetry and SLAM-Based Survey Approach

Abstract. Digital access to archaeological and cultural heritage sites is increasingly important for research, conservation, and public dissemination. This paper presents a hybrid survey strategy combining Unmanned Aerial Vehicle (UAV) photogrammetry and Portable Laser Scanning (PLS) based on Simultaneous Localization and Mapping (SLAM) technology for the documentation of the Ain Akrine archaeological site (Koura region, northern Lebanon), a vegetated hilltop area hosting the Roman Qasr Naous temples. The proposed multi-sensor approach enables the generation of site-scale orthophotos and surface models, detailed photogrammetric reconstructions of the temples, and a SLAM-derived point cloud providing continuous coverage of the entire area, including densely vegetated zones. The integration of multiple PLS acquisitions with photogrammetric datasets results in a spatially consistent and multi-scale 3D representation. Quantitative accuracy analyses confirm the high reliability of the photogrammetric products and demonstrate that the SLAM-based survey achieves accuracy levels consistent with the expected performance of the adopted sensor, despite the absence of external constraints. The results highlight the effectiveness and flexibility of hybrid UAV–PLS approaches for comprehensive archaeological documentation under challenging environmental and logistical conditions.