Titolo della tesi: Satellite Differential Interferometry (DInSAR) for Ground deformations and Transport infrastructure monitoring
The increasingly use of Earth Observation (EO) techniques for the study of ground displacements and civil infrastructure monitoring proceeds in parallel with the development of geospatial technologies and the availability of satellite images. The scientific knowledge acquired together with the ability to disseminate timely geospatial information is contributing to a comprehensive planning of risk mitigation and a better response to the phenomena that cause land displacement. The spaceborne is a highly strategic sector, which is having an important impact on the management of territory and civil infrastructures, the interest of the scientific community in using satellite sensors extends from research, to the manufacture and use of focused tools to services, through iCloud platforms for processing satellite images and data analysis.
The use of SAR (Synthetic Aperture Radar) satellite images, together with different image processing techniques, have been used in this study to detect the land and civil infrastructures displacement. Image processing techniques and algorithms have been developed in the electronic engineering and telecommunications sector, however the field of application is mainly the civil and environmental engineering and geology. In this context, differential interferometry technology with the use of data acquired through Synthetic Aperture Radar, (DInSAR) is one of the most advanced satellite techniques that allows the stability of buildings and infrastructures to be monitored with millimeter and / or centimeter precision.
In recent decades, the open data policy and the trend towards free access to a large number of images from space sensors such as ERS, Envisat and Sentinel-1 from ESA (European Space Agency), has facilitated access to information to promote the growth of the geospatial industry, whether for commercial or academic use. On the other hand, the technological contribution stands out, where Italy excels with the COSMO-SkyMed mission of the ASI (Agenzia Spaziale Italiana), composed of two constellations in orbit, the first generation launched in 2007, and the second generation launched in 2019, both cases represent the pinnacle of SAR observation from space in terms of accuracy, characteristics and image quality. As technology improves, expectations for near real-time natural hazard assessment increase due to improvements made to satellite platforms, as well as the reliability of image processing and analysis algorithms.
This thesis work represents the main result of a three-year activity in the Department of Civil Engineering, Construction and Environment of the Sapienza University of Rome, its objective is to test and evaluate the potential and applicability of SAR data, for the monitoring of land displacements and infrastructures, using different approaches, as operational tools for the characterization of subsidence in civil infrastructures and in different environments. A case study in Italy is presented, the objective of which is to transfer skills to a case study in Chile, where different approaches are shown aimed at reconstructing the history of surface deformations mainly related to subsidence, evaluating the impact and areas of displacement detected and elements at risk in the urban context and road infrastructures.
In this Doctoral thesis, the potentialities of different tools based on Differential SAR Interferometry (DInSAR) have been presented and then exploited to define procedures applied in different geological environments and at different scales, for the use of multiband SAR products. To achieve mastery of this research, state-of-the-art tools were used, such as the I.MODI platform - Satellite Service for Structural Monitoring, developed by the Survey Lab Spin-off of DICEA Sapienza and Geohazard TEP, which is part of ESA's Thematic Exploitation Platform program and supported by the ESA NoR (Network of Resource) project - Chile ID: 65514.
In addition, a methodology is presented for the analysis of subsidence in the transport infrastructure network of Metropolitan Rome, based on the classification of the average velocity displacement of the highway sections, and the study of the deformations acquired at the network scale. The idea is to start from a dataset made up of a large volume of data (PS measurement points) and to recognize those areas that present high rates of displacement or anomalous changes in their temporal behavior, based on the time series. In conclusion, the PSI data demonstrated its suitability for different geological environments, and for different types of structures in the case of transport infrastructures, the results obtained open new research horizons in the field of monitoring and maintenance and management of infrastructures.