SAR interferometry with open Sentinel-1 data for environmental measurements: The case of Ischia earthquake

This study rely on open access data as well as open software, both provided by the European Space Agency (ESA) under the Copernicus program. In particular, data from Sentinel-1 radar satellite mission and SNAP software have been used. The availability of such data and software is relevant for public institutions that can produce valuable information at almost no charge. Main aim of the authors has been to produce a review paper, a kind of tutorial, where main characteristics of Sentinel-1 data and SNAP processing tools are presented and discussed. It's important to underline that SNAP is not an easy tool and needs a deep knowledge of electromagnetic aspects to result into reliable results. Together with Sentinel-1 data, interferometry techniques have been employed to get from phase difference information a measure of ground displacements. The Ischia island has been chosen as Case Study because it was affected by a severe earthquake in August 2017. In the days following the earthquake, the area was subject to many topographic surveys. Some of them, carried out by CNR-IREA researchers [1], working in collaboration with INGV, have used DInSAR technique applied to Sentinel-1 and COSMO-SkyMed images, showing a lowering of the soil around the epicenter up to 4 cm [2], [3]. These data have been used in our processing for comparison and validation as explained later in the paper.