La cattedrale di San Lorenzo a Perugia e gli ambienti ipogei del Museo del Capitolo. il rilievo digitale per la conoscenza e l’interpretazione di insiemi architettonici complessi

The aim of this research is to complete gradually the survey the monumental complex of the Capitolo of San Lorenzo, still ongoing, with particular attention to the church, the attic, the upper courtyard and the lower one, including the hypogeal rooms of the Capitular Museum, where important and impressive ruins as a portion of Etruscan terracing walls are present. The complex is extremely articulated, so it was necessary to correlate external and hypogeal internal spaces located at different levels throught the coordinated and integrated use of geomatic techniques: detailed surveys performed with laser scanning, photogrammetry and precision GNSS positioning with the creation of a very articulated three-dimensional geodetic network connecting the external GNSS vertices with the internal reference points and targets in order to assemble the single scans and local surveys into a unique georeferenced point cloud. The high-definition 3D model obtained allows to extract multiple information both structural and archaeological and to conduct studies with a multiscale approach, which may concern limited parts of rooms, individual objects, or the entire complex. Among the various aspects highlighted, it was possible to understand in more detail the conformation and genesis of both the transept of the cathedral and the adjacent Capitolo courtyard.