Abstract
Space-borne Synthetic Aperture Radar (SAR) Interferometry (InSAR) is now a key geophysical tool for surface deformation studies. The European Commission’s Sentinel-1 Constellation began acquiring data systematically in late 2014. The data, which are free and open access, have global coverage at moderate resolution with a 6 or 12-day revisit, enabling researchers to investigate large-scale surface deformation systematically through time. However, full exploitation of the potential of Sentinel-1 requires specific processing approaches as well as the efficient use of modern computing and data storage facilities. Here we present Looking Into Continents from Space with Synthetic Aperture Radar (LiCSAR), an operational system built for large-scale interferometric processing of Sentinel-1 data. LiCSAR is designed to automatically produce geocoded wrapped and unwrapped interferograms and coherence estimates, for large regions, at 0.001° resolution (WGS-84 coordinate system). The products are continuously updated at a frequency depending on prioritised regions (monthly, weekly or live update strategy). The products are open and freely accessible and downloadable through an online portal. We describe the algorithms, processing, and storage solutions implemented in LiCSAR, and show several case studies that use LiCSAR products to measure tectonic and volcanic deformation. We aim to accelerate the uptake of InSAR data by researchers as well as non-expert users by mass producing interferograms and derived products.
Highlights
With the advent of the European Commission’s Copernicus two-satellite Sentinel-1 constellation, operated by the European Space Agency (ESA), a massive volume of high-quality C-band Synthetic Aperture Radar (SAR) observations with moderate spatial (2–14 m) and temporal resolution (6–12 days) has become freely available [1]
The basic Interferometric Synthetic Aperture Radar (InSAR) products generated by LiCSAR are original and spatially-filtered wrapped, as well as unwrapped, interferograms and original coherence maps, MLI images for each epoch, and complementary specialised frame images, including incidence angle map files needed for motion vector extraction [49], height values from the DEM used in processing, preprocessed Generic Atmospheric Correction Online Service (GACOS) products, and metadata information
The unit vector information can be used, for example, to project E-N-U modeling results or 3-dimensional geodetic observations like GNSS data onto the LOS vector in order to be able to compare them to the LiCSAR results [43]: OOOP_AAAAA_BBBBBB.geo.hgt.tif: this image (GeoTIFF) contains the height values extracted from the DEM used in processing; baselines: a text file containing the temporal and spatial baselines of each acquisition with respect to the master image; metadata.txt: a text file containing various other information related to the frame In the near future, the time-series and velocity folders will contain outputs stemming from multitemporal InSAR processoring based on the LiCSBAS tool [64]
Summary
With the advent of the European Commission’s Copernicus two-satellite Sentinel-1 constellation, operated by the European Space Agency (ESA), a massive volume of high-quality C-band Synthetic Aperture Radar (SAR) observations with moderate spatial (2–14 m) and temporal resolution (6–12 days) has become freely available [1]. We present activities carried out for the design, development, integration, and deployment of a fully automated state-of-the-art InSAR processing chain for Sentinel-1 data developed within the Looking Inside the Continents from Space (LiCS) project by the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET). The LiCS project primarily aims at understanding how the continents deform at all spatial and temporal scales, with a focus on using observations of the earthquake deformation cycle to understand how seismic hazard is distributed in space and time For this purpose, an automated InSAR processing system, LiCSAR, has been developed. LiCSAR is capable of processing Sentinel-1 data acquired globally, with the resulting products freely accessible and downloadable through an online portal, including both wrapped and unwrapped interferograms, coherence estimates, time series and other products. As Appendix A, we include a list of abbreviations and brief explanation of external commands mentioned throughout the article
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