Sustainable preservation strategies for street art (SUPERSTAR) through the integration and comparison of hyperspectral techniques at close and ultra-close range

In recent years, street art has been recognised as a form of cultural heritage. However, its ephemeral nature, coupled with continuous exposure to environmental and anthropogenic factors such as vandalism, pollution, and urban development, poses significant challenges for its documentation, conservation, and long-term preservation. These challenges are further compounded by the often inaccessible or large-scale urban surfaces on which street art is created, requiring flexible, noninvasive, and high-resolution monitoring techniques. In response, this study presents a multi-modal approach that integrates hyperspectral imaging (VIS-NIR) and thermal imaging from unmanned aerial vehicles (UAVs), laser scanners and ground hyperspectral instrumentation to analyse four mural works in Turin and Milan. In a 4-hour flight, an extremely high spatial resolution hyperspectral and thermal dataset was acquired, covering over 850m² of surface area. The images, calibrated and subsequently geometrically corrected by laser scanner, were then compared with ground data from high specific spectroscopic point analyses and hyperspectral imaging, classified with Spectral Angle Mapper (SAM). The results highlight the potential of using UAVs to study large wall surfaces, the speed of acquisition in complex contexts and the possibility of extending this technique, contributing to new strategies for the conservation and management of street art.