Necropolis of Palazzone in Perugia: Geomatic data integration for 3D modeling and geomorphology of underground sites

This article presents and analyzes the methodologies and results of the survey of an Etruscan archaeological site (the Necropolis of Palazzone) with tombs dug into the ground on a slope belonging to the Perugia hill, in central Italy. The survey presented particular difficulties, since the underground rooms are numerous, small, and not illuminated, and it required the creation of a unique geometric model, including both the underground and the external area. Therefore, different techniques and tools of geomatics were used: GNSS, total station 3D survey, terrestrial laser scanning, and digital photogrammetry, with the consequent need to manage and integrate a large amount of data. It was also possible to compare the results acquired with different methods, such as the digital terrain model of the external surface obtained by unmanned aerial vehicle photogrammetry or by kinematic GNSS survey. The survey had a dual purpose: to acquire documentation of the archaeological site geometry to be imported into GIS; and to support knowledge of the geomorphologic aspects of the area, as the tombs—carved into the sedimentary formations—allow us to observe and study the local stratigraphy in detail, while the geomatic surveys put the rooms in geometric relation to each other in 3D space.