Multisource 3D Analyses for the Detection and Documentation of a Submerged Defensive System: The Vallo Alpino Littorio in the Gardetta Plateau Area (CN)

The main purpose of this work is to enhance the potentiality of heterogeneous documentation integrating both bibliographic and archival sources with different innovative data acquisition technologies and the contribution of GIS environment in data management, correlation, and analysis. The experience considered three World War II Opere and two military roads, surveyed combining UAV photogrammetry and terrestrial scanning solution, from SLAMbased mobile system. These techniques allowed to obtain accurate and precise modelling of these structures that has been integrated, in the missing parts, with a previous traditional survey, stored by Primo Reparto Infrastutture archive of Torino. Additionally to data merging and integration of image and range-based products and current and historical cartography, the geomatic data fusion approaches allowed to perform different analyses for holistic landscape knowledge in GIS environment. This was achieved by exploiting archive documents and bibliographic studies on the architectural and weaponry projects of the Opere as well as their connection with the alpine landscape and, specifically, with the military road system, built upon the historical alpine mule-tracks. The analysis strategy has been applied to the Gardetta Plateau area in upper Maira Valley (CN), which, between XVIII and XX centuries, has been the object of a series of transformations for the realization of different defensive systems, to protect Regno di Sardegna, first, and Italy, after. These projects had a great impact on the landscape and, nowadays, even if scarce remains are left from the eighteenth-century entrenchments, the so-called Opere in caverna and the military roads, realized for World War II as part of the Vallo Alpino Littorio defensive system, are still existing, accessible and practicable, even if abandoned and not well preserved in certain parts. Due to its unfavourable geographical position, this military heritage, embedded in an alpine well-preserved landscape, nowadays is unknown and needs great attention and valorisation, starting from the knowledge and metric documentation processes in which techniques related to geomatics often contribute significantly.