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Satellite Interferometric Synthetic Aperture Radar (InSAR) is widely used for topographic, geological and natural resource investigations. However, most of the existing InSAR studies of ground deformation are based on relatively short periods and single sensors. This paper introduces a new multi-sensor InSAR time series data fusion method for time-overlapping and time-interval datasets, to address cases when partial overlaps and/or temporal gaps exist. A new Power Exponential Knothe Model (PEKM) fits and fuses overlaps in the deformation curves, while a Long Short-Term Memory (LSTM) neural network predicts and fuses any temporal gaps in the series. Taking the city of Wuhan (China) as experiment area, COSMO-SkyMed (2011–2015), TerraSAR-X (2015–2019) and Sentinel-1 (2019–2021) SAR datasets were fused to map long-term surface deformation over the last decade. An independent 2011–2020 InSAR time series analysis based on 230 COSMO-SkyMed scenes was also used as reference for comparison. The correlation coefficient between the results of the fusion algorithm and the reference data is 0.87 in the time overlapping region and 0.97 in the time-interval dataset. The correlation coefficient of the overall results is 0.78, which fully demonstrates that the algorithm proposed in our paper achieves a similar trend as the reference deformation curve. The experimental results are consistent with existing studies of surface deformation at Wuhan, demonstrating the accuracy of the proposed new fusion method to provide robust time series for the analysis of long-term land subsidence mechanisms. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) of engineered structures consists of an automated or semi-automated survey system that seeks to assess the structural condition of an anthropogenic structure. The aim of an SHM system is to provide insights into possible induced damage or any inherent signals of deformation affecting the structure in terms of detection, localization, assessment, and prediction. During the last decade there has been a growing interest in using several remote sensing techniques, such as synthetic aperture radar (SAR), for SHM. Constellations of SAR satellites with short repeat time acquisitions permit detailed surveys temporal resolution and millimetric sensitivity to deformation that are at the scales relevant to monitoring large structures. The all-weather multi-temporal characteristics of SAR make its products suitable for SHM systems, especially in areas where in situ measurements are not feasible or not cost effective. To illustrate this capability, we present results from COSMO-SkyMed (CSK) and TerraSAR-X SAR observations applied to the remote sensing of engineered structures. We show how by using multiple-geometry SAR-based products which exploit both phase and amplitude of the SAR signal we can address the main objectives of an SHM system including detection and localization. We highlight that, when external data such as rain or temperature records are available or simple elastic models can be assumed, the SAR-based SHM capability can also provide an interpretation in terms of assessment and prediction. We highlight examples of the potential for such imaging capabilities to enable advances in SHM from space, focusing on dams and cultural heritage areas.

Optical and Synthetic Aperture Radar (SAR) remote sensing has a long history of use and reached a good level of maturity in archaeological and cultural heritage applications, yet further advances are viable through the exploitation of novel sensor data and imaging modes, big data and high-performance computing, advanced and automated analysis methods. This paper showcases the main research avenues in this field, with a focus on archaeological prospection and heritage site protection. Six demonstration use-cases with a wealth of heritage asset types (e.g. excavated and still buried archaeological features, standing monuments, natural reserves, burial mounds, paleo-channels) and respective scientific research objectives are presented: the Ostia-Portus area and the wider Province of Rome (Italy), the city of Wuhan and the Jiuzhaigou National Park (China), and the Siberian "Valley of the Kings" (Russia). Input data encompass both archive and newly tasked medium to very high-resolution imagery acquired over the last decade from satellite (e.g. Copernicus Sentinels and ESA Third Party Missions) and aerial (e.g. Unmanned Aerial Vehicles, UAV) platforms, as well as field-based evidence and ground truth, auxiliary topographic data, Digital Elevation Models (DEM), and monitoring data from geodetic campaigns and networks. The novel results achieved for the use-cases contribute to the discussion on the advantages and limitations of optical and SAR-based archaeological and heritage applications aimed to detect buried and sub-surface archaeological assets across rural and semi-vegetated landscapes, identify threats to cultural heritage assets due to ground instability and urban development in large metropolises, and monitor post-disaster impacts in natural reserves. [ABSTRACT FROM AUTHOR]

Satellite radar remote sensing techniques are non-invasive methodologies that can be effectively used for diagnostic purposes, measuring displacements, and monitoring cultural assets, architectural structures, and archaeological areas without injuring their integrity. The environmental condition and hydrogeological hazard in the Italian territory could make its invaluable Cultural Heritage at risk. Therefore, within the National Extraordinary Plan for Monitoring and Conservation of Cultural Heritage, an agreement has been established between the Ministry of Culture and the UNESCO Chair of the UNiversity of Florence on Prevention and Sustainable Management of Geo-hydrological Hazard to analyse ground motion rates on built-up areas by means of acquisition and PSI (Persistent Scatterers Interferometry) elaboration of high-resolution CosmoSkyMed synthetic aperture radar (SAR) satellite data (X-band). This technique can provide useful support on the conservation and protection of Cultural Heritage, as it endorses an innovative perspective on the condition and safety of historical sites, monuments, archaeological sites and artworks, thus contributing significantly to their preservation over time. Through SAR interferometric techniques, it is possible to identify millimetric displacements related to environmental threats, such as slow-moving landslides. This work proposes the classification of buildings of urban areas by using two indices based on PSI data coverage and deformation rates: the data coverage index in each building (Id) and the average velocity index of PSI data in each building and its surroundings (Ivmean), representing deformation rates in a locally scaled, easily understandable color-coded format. This method has already been tested in scientific literature on other SAR datasets for evaluating instability at the building scale. The approach aims to develop a fast and low-cost system to assess buildings that are potentially exposed to deformation and therefore more susceptible to damage in heavily urbanized areas with high historical-cultural value. In order to safeguard Cultural Heritage from natural disasters, the proposed methodology integrates a high degree of scientific and technological expertise and presents an updated and accurate screening of potential deformations due to hydrogeological hazards. [ABSTRACT FROM AUTHOR]

Earth Observation (EO) is nowadays a primary source of geospatial data to address urban applications. As information layers imported into GIS, EO products are increasingly exploited for cartographic purposes to improve cities representation. The Italian Space Agency (ASI) invests in novel satellite-based applications and digital tools facilitating EO data utilization. Such tools include: thematic exploitation platforms enabling EO data processing by nonexpert users through validated processors; dashboards wherein satellite products are among the input data used during the decision-making process; Digital Twins allowing for what-if scenarios and forecast activities. Recent user-driven developments are presented with regard to urban heat island, coastal applications, conservation of cultural heritage, monitoring and modelling of processes related to terrestrial water cycle. [ABSTRACT FROM AUTHOR]