A collaboration between Geocento and NHAZCA, sponsored by the Erasmus Traineeship program and directed by the University of Rome ‘Sapienza’, gave me the opportunity to spend three months working at Geocento. During this period I learned how best to exploit Geocento technology for imagery search in support of synthetic aperture radar interferometric (InSAR) applications. Nowadays, the multi-image A-DInSAR (Advanced Differential InSAR) method is considered a powerful technique, allowing the identification of multi-temporal surface deformation processes with accuracies of the order of millimetres and to achieve time series of displacement both for wide areas and for single buildings or structures. Such capabilities make InSAR a suitable tool for several key applications including monitoring of subsidence processes (e.g. due to oil and gas extraction), slope stability assessment, structure/infrastructure monitoring (i.e. dams, buildings, highway, viaducts, etc.), tunneling-induced ground deformation monitoring, land use planning, monitoring of volcanic and seismic activity, etc.
Sentinel-1 interferogram of the Amatrice earthquake (24th August 2016, Mw 6.0, 01:36:32 UTC). Images were acquired on 15/08 – 27/08 from an ascending orbit pass. One fringe (colour cycle) corresponds to a displacement of 2.8 cm in the line of sight direction. The configuration of the “fringes” shows the pattern of ground disruption caused by the earthquake. The magnitude 6.2 earthquake was felt across central Italy and killed about 300 people.
Thanks to past and present satellite missions, a large and growing quantity of satellite imagery is available for InSAR. On the flip side, the growing number of suppliers and satellite missions can make the search for imagery complex and time-consuming. A particular challenge for all InSAR applications lies in identifying which radar imagery is suitable, as not all such imagery can be used. With this in mind, Geocento’s EarthImages platform is a unique tool, allowing the user to efficiently find optical and radar imagery from the majority of existing satellites (TerraSAR-X and TanDEM-X, Radarsat-1 and Radarsat-2, Sentinel-1, KOMPSAT-5, etc.) while at the same time being able to filter the imagery using a range of constraints. The EarthImages Pro platform in particular can handle a very large range of product metadata parameters and this is crucial for evaluating the feasibility of InSAR applications, which relies on a large number of suitable images recorded over an extended time period.
The availability of suitable satellite data is the basic requirement for the application of the InSAR technique. The benefits of an efficient process of data discovery and selection for InSAR include not only highly valuable products, but also efficient interactions with clients and lower costs (in terms of time spent in image sourcing and selection) of service provision.
During my internship, and both before and after, I often used the EarthImages Pro platform to search for the most suitable imagery to be analyzed with InSAR. In particular, I made use of an advanced tool from Geocento (namely the Grouping tool) that allowed me to quickly select and extract the images that had particular configurations and attributes suitable for InSAR. A necessary condition in performing interferometric analyses is to use only radar images acquired with the same geometry and features (i.e., only images in ascending or descending orbit, same incidence angle, same resolution, same polarization, etc.). I was able to configure the grouping tool to take these image selection constraints into account and thus to identify so-called data-stacks that can be processed using InSAR techniques.
Geocento, Nhazca, University of Roma Sapienza would like to that the Erasmus program for their sponsoring of the internship.