## 1 Introduction
Furthermore, the use of advanced DInSAR approaches [37; 38; 39; 40; 41; 42], based on the exploitation of SAR acquisition sequences collected over large time spans, allows the provision of useful information on both the spatial and the temporal patterns of the detected displacements through the generation of time series, with centimeter to millimeter accuracy [43; 44; 45]. The advanced DInSAR techniques allow to map and measure deformation phenomena due to both natural and anthropic causes [46; 47; 48; 49; 50; 51; 52; 53; 54] with limited monitoring costs compared to the traditional in situ surveys. Furthermore, these techniques represent a non-invasive tool to remotely detect, map and monitor deformation phenomena affecting urban areas by providing velocity maps and displacement time-series, for a large number of measurement points and long observation periods [55]. DInSAR techniques have also demonstrated the capability to provide valuable information on the displacements affecting single buildings (see, for instance [56; 57]). Thanks to their capability to extend backwards by exploiting the SAR data archives available since the early ERS-1 ESA mission in 1992, the DInSAR investigations allow comparisons of pre- with post-event conditions and contribute to the implementation of damage assessment analyses and to the evaluation of risk scenarios [56; 57; 58; 59; 60]. The multi-temporal Small Baseline Subset (SBAS) DInSAR technique allows the investigation and mapping of ground movements through the generation of mean deformation velocity maps and corresponding displacement time series [38; 39; 40]. It relies on a proper selection of a large number of SAR image pairs characterized by short spatial and temporal separations (referred to as baseline) between the acquisition orbits, in order to mitigate decorrelation phenomena and to maximize the number of reliable (coherent) SAR measure points [61]. In particular, the deformation time series are computed by searching for a least square solution with a minimum norm energy constraint [38]. Moreover, by contrast with other advanced multi-temporal DInSAR techniques, the SBAS approach does not need any _a priori_ information on the investigated ground deformation phenomena, thus representing a valuable method to detect and measure non-linear LOS displacements over time. The SBAS-DInSAR technique is able to work at two different spatial resolution scales, referred to as regional and local scale analyses. In the regional scale, the algorithm is able to produce deformation maps of wide areas (up to 250 \(\times\) 250 km\({}^{2}\)) with a ground spatial resolution ranging from about 30 to 100 m, suitable to natural wide-area deformation events. At the local (full resolution) scale, the SBAS approach exploits single-look interferograms, generated at the full sensor spatial resolution (down to a few meters), to study local deformation that may affect buildings and man-made features [39; 40]. The SBAS approach allows generation of LOS displacement maps and associated time series spanning very long periods (decades), thus guaranteeing the continuity in the monitoring of the Earth's surface deformation phenomena, as well as providing unprecedented information for studying long-term ground movements at different spatial scales. At the local scale, these measurements can contribute to the evaluation of the structural conditions of the single constructions.