On the combined use of satellite and on-site information for monitoring anomalous trends in structures within cultural heritage sites

Existing structures and infrastructures are exposed worldwide to different types of hazards during their service life, such as earthquakes or landslides, especially in countries characterized by high seismicity and hydrogeological risk, as Italy. Mitigation risk and safeguarding existing structures are tasks of great interest for structural engineering. Recently, advanced multi-temporal differential synthetic aperture radar interferometry (DInSAR) products have been used to monitor the evolution in time of ground movement that affects structures. This paper proposes a methodological approach to integrate DInSAR data, visualized in the GIS environment, with on-site measurements. DInSAR and terrestrial laser scanning (TLS) are purposely combined to facilitate the spatial interpretation of displacements affecting cultural heritage sites. An insight into the proposed approach is provided through the study of the Capitoline Museums in Rome (Italy) focusing on Marcus Aurelius Exedra, by exploiting the data archive (ascending and descending acquisitions) collected during the 2012-2020 time interval. Identifying possible critical situations for the analyzed structure is carried out through the analysis of DInSAR-based displacements time series and mean deformation velocity values. Ascending and descending data are combined to extract the components of ground motions and reveal the presence of predominant components in the vertical direction. This is also confirmed by comparing the "as-build" model (obtained from TLS) and the "as-design" model (obtained from the original technical drawing). Therefore, the DInSAR-TLS combination allows supporting structural health monitoring early warning procedures of structures.