Displacements with remote sensing and standard ground survey for the Benedictine Basilica of S. Angelo in Formis (Southern Italy).

Cultural and historic buildings, such as ancient palaces, churches, tombs and bridges are rare and irreplaceable wealth of human civilization. Unfortunately, they are often impacted by natural calamities and anthropogenic activities. The former includes landslides, earthquakes, floods, adverse weather and abrupt climate change. However, more serious and increasing threats could originate from wars, overexploitation, urbanization and uncontrolled tourism. Consequently, the monitoring and preventive diagnosisof structure’s deformation, as well as their surroundings, are essential for their safeguarding and conservation. Highprecision and efficient monitoring facilitates the early recognition of potential risksand enables preventive diagnosis of heritage sites. This work shows the potential interest of using remote sensing technique as a complementary tool for the analysis of the movements of Benedictine Basilica of S. Angelo in Formis, and important monumental building in the area north of Napoli in Southern Italy. Geological survey of the area, subsoil investigations and the integrated analysis of remote sensing and geodetic data, allows to perform a very careful and detailed investigation about the structural performance of the Basilica and also support the possibility of a correct diagnosis needed for establishing the best therapy to protect either the monument and the frescoes on the inside walls from cracks and damages. In detail, Differential Synthetic Aperture Radar (DInSAR) data have permitted a global interpretation of the Basilica’s deformation and its surrounding areas. Firstly, they have been successfully applied as a tool to detect spatial and temporal effects on the whole area, relate to the ground instability. Subsequently, C-band and X-band products, available starting from 1992, have been integrated with topographic measurements, thus confirming the occurrence of differential settlements of the monument. Moreover, historical DInSAR data have permitted the interpretation of building displacement time-series, and than the assessment of gradient maps of vertical and horizontal displacements, useful to identify part of structure which could suffer a greater susceptibility to damage as a consequence of deformation gradients.