Combined techniques for the stability control of historical structures

The demand for high-definition surveys within cultural heritage-related projects represents one of the main factors which promoted the use of laser scanning technology. By measuring millions of points within relatively short time periods, terrestrial laser scanners allows to derive complete and very detailed 3D models of real objects from acquired point clouds. These features drew in recent years the interest of surveyors, engineers, architects and archaeologists towards the laser scanning technique as an invaluable surveying mean for 3D modeling of sites and artifacts of cultural heritage. A wide variety of objects, e.g., small pieces of pottery, statues, buildings, and large areas of archaeological sites, have been scanned and modeled for various purposes like preservation, reconstruction, study, and museum exhibitions. However, the use of TLS systems for stability control is still a research field not much investigated. In the view of insight investigation on this topic, a three-years project has been established in order to evaluate the use of multiple surveying techniques for the stability control of a complex historical structure. To this aim, terrestrial laser scanning (TLS), total station (TS), deflectometers and photogrammetry are being employed for a first test on the Anatomy Theatre, one of the oldest, most important and best-known historical \u201cmedical\u201d buildings. Located inside the Palazzo del Bo\u2019, the building seat of the University of Padua, the Theatre was built in 1594 as first permanent structure of its kind and substituted for the temporary theatres which were set up when necessary. The main goal of this work is to verify the stability over the time of this kind of structure, given the inherent organic decay of the wooden parts. So far three consecutive surveys of the Theatre have been carried out with a Leica laser scanner (HDS 3000) and a Leica Total Station. In the first one the historical structure has been fully measured in order to derive a complete 3D model suited for FEM analysis; then, according to a six months time span, two further surveys were performed for stability check. In this paper we present the results obtained from the repeated surveys and highlight issues and difficulties related to the laser scanning of an unusual geometry such as the one provided by the Anatomy Theatre of the University of Padua