“Mura della Bastia” – Onigo di Pederobba (Treviso). Ricerche archeologiche, rilievo 3D laser scanning e anastilosi virtuale in un castello medievale del pedemonte trevigiano

The paper presents the results of the ongoing research coordinated by the Chair of Ancient Topography at the University of Padova. The work concerns the medieval site of “Mura della Bastia” in Onigo di Pederobba (Treviso), in the North-Eastern part of Italy. Historical information from written documents and results obtained from the archaeological investigation at the Onigo castle (1994-2007) are discussed. The study provided the historical reconstruction of recent collapses of the Onigo tower and allowed the virtual reconstruction of still-cohesive blocks, which had fallen down in 1989, and which were recovered during the summer of 2007. At this time, five of the ten building blocks have been positioned; the procedure was carried out by comparing the panoply of each agglomerate with the prospect of the tower, which was obtained from the photogrammetric rectification of the historical images (2D). The 3D survey of the tower and of nine blocks was performed with a Leica HDS 2500 laser scanner. The resulting point clouds were aligned with Cyclone software, also using the coordinates of some laser scanning targets, which were measured with the Leica TC 2003 total station in a local reference system. The final 3D model obtained by the co-registration of the scans was textured with the digital images acquired with a Canon EOS 1 ds Mark II camera. Subsequently, three of the five recognized blocks were positioned on the 3D model using Reconstructor software