Digital survey and representation for built historical heritage protection. The case of Gerace (Reggio Calabria)

Historic centers contain a large amount of unquantified cultural heritage that today is often considered at risk. Due to their nature and intrinsic characteristics, they require protection and safeguard interventions. This article describes how representation, considered as a knowledge process based on architectural survey and 3D modeling, constitutes a fundamental instrument of investigation. Digital survey allowed to collect and systematize a large amount of information related to the oldest part of the historic center of Gerace, a medieval historic centre located in the province of Reggio Calabria (Italy). The work is part of a larger research project, called GENESIS (acronym for Seismic risk management for the tourist enhancement of the historic centers of Southern Italy), promoted by several research groups from numerous Italian universities. The main goal of the project is to promote safe and informed use of cultural heritage, starting from a deep understanding of their history and characteristics, and to encourage accessibility to places and monuments by visitors, scholars, and tourists through innovative forms of management and dissemination. The work conducted in Gerace concerns urban, architectural, and detailed scales. In this context, we present the work carried out using aerial photogrammetry by UAVs, and its possible developments. The instrumental survey, carried out at different levels of detail (entire historic center, urban area, single building, morphostructural and decorative elements), was a fundamental tool for starting subsequent investigations, in particular: • analyses related to the seismic risk of the settlement; • structural assessment of single buildings; • study of the characteristics of the materials used for construction, and study of degradation. The graphic representations of the surveys were essential for the implementation of the platform that collects all the project data (https://genesis.tabsrl.com/) and for the creation of virtual tours of the historic center and the main monuments within it.