Geometric and Radiometric Analysis of TLS Point Clouds to Diagnose the Conservation State of Historical Constructions. Case of Study in the Master Gate of San Francisco, Almeida, Portugal

This paper summarizes the experimental results obtained after the radiometric and geometric analysis of the 3D point cloud model of one of the most emblematic constructions inside the Fortress of Almeida (Portugal): the Master Gate of San Francisco. The data acquisition was performed with a Faro Focus 120 Terrestrial Laser Scanner previously calibrated. The evaluation of the construction involved the combination of both approaches through the use of K-Means unsupervised classification approach, the Efficient RANSAC Shape Detector and the CANUPO algorithms. As a result, an accurate identification of a wide diversity of indicators of damage (salt crusts, black crusts and deformations, among others) was achieved. The results of the proposed semi-automatic methodology have allowed, in a non-intrusive way, a robust identification of the different degradation mechanisms that are promoting the blistering of that construction’s masonry.