Speaker
Description
This paper presents a multi-source point cloud methodology for the conservation state monitoring and three-dimensional documentation of the defensive walls of the Historic Town of Mértola, Portugal. Two Terrestrial Laser Scanner (TLS) campaigns conducted with a 5-month interval were compared to detect and map inter-annual structural displacements along a critical wall section. A partial wall collapse recorded in the winter of 2025 was documented through a UAV photographic survey of the area, whose data were merged with the TLS dataset to reconstruct the pre-repair geometry and quantify the volume of lost material, demonstrating the value of point cloud-based methods for assessing damage in historic masonry. Complete 3D models of two wall sections were generated by integrating TLS, UAV photogrammetry, airborne LiDAR data and 360º spherical imagery, overcoming the geometric limitations of each individual technique. Additionally, a controlled metrological experiment using a test object of known geometry is presented to characterise the influence of scanner viewing angle and range on point cloud quality, providing a quantitative basis for interpreting displacement measurements in complex survey configurations.