Satellite Radar Interferometry for monitoring historic urban fabric: Lucca and Florence test cities

Satellite radar interferometric techniques are non-invasive remote sensing methods without material contact with manufacts and with high data sampling, so that they can be profitably used for measuring and periodically monitoring millimetric deformations of architectural structures without affecting their integrity. In particular, this work proposes a procedure for detecting and monitoring ground movements based on Synthetic Aperture Radar Interferometry (InSAR) data elaborated through Persistent Scatterers Interferometry (PSI) technique over historical built-up areas. We exploit PSI data extracted from medium resolution Sentinel-1 satellite images acquired in the time span 2014–2021 to analyse deformation patterns and potential instability of single building at local scale, with particular attention to Cultural Heritage structures. The analysis was performed on two test cities: Florence city, whose historic centre enclosed within the avenues that follow the old medieval walls is recognized as a World Heritage Site by UNESCO since 1982, and Lucca city, whose historic centre was submitted to the UNESCO Tentative List in 2006. Results demonstrate the potential use of remote sensing satellite technologies in measuring deformation phenomena on historical buildings, especially in areas affected by hydrogeological hazards, such as subsidence and slow-moving landslides. In particular, the outcomes of such PSI monitoring could be a useful tool to be considered for authorities in charge of environmental planning in addressing urban zoning regulations and prescribing maintenance and improvement of the heritage and historic city centre resilience.