LiCSAR: An Automatic InSAR Tool for Measuring and Monitoring Tectonic and Volcanic Activity

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.

Displacements Monitoring over Czechia by IT4S1 System for Automatised Interferometric Measurements Using Sentinel-1 Data

“…Whereas common HPC approaches of utilising Sentinel-1 images for InSAR start their processing chain from either original SLC data or raw non-coregistered data [46], the IT4S1 system allowed a faster and more flexible multitemporal processing thanks to availability of specifically pre-processed SLC C ARD images, based on ISCE/ISCE2 [7,8]. As these ARD already do not contain most of the phase induced by topography, Earth curvature, etc., there is no need to simulate and remove the topography and orbital ramp components per each generated interferogram, as typically done in other InSAR-oriented systems, e.g., LiCSAR [17]. The SLC C ARD proved its quality and effectivity to be used for a typical InSAR processing toward deformation monitoring.…”

“…After the ingestion of a new Sentinel-1 SLC acquisition to CollGS, a metadata database system solution transferred from LiCSAR [17] ensures a proper identification of its bursts including information about their geographic coverage. When activated, the SLC preprocessor loads the SLC data with the latest available ephemeris data and splits it into bursts.…”

“…As the first step, a systematic data storage environment is established, aiming for the data storage structure: RELORB/SWATH/BURST_TANX/YEAR, where RELORB is a relative orbital track number of Sentinel-1 satellites, SWATH is a number from 1-3 identifying one of the three Sentinel-1 swaths, BURST_TANX is a burst identifier based on a naming convention established by LiCSInfo approach of the LiCSAR system [17]. In order to avoid large number of files in BURST_TANX folder, we sort them in subfolder YEAR (year of acquisition date).…”

“…We keep outputs of both processing techniques separate in order to allow for comparison of results. For STAMPS SB MT-InSAR, we form the network of SB interferograms in the fashion of combining each SLC C image with four following dates, as described by the authors of [17]. The estimated deformation values are inverted toward the same reference date as used for STAMPS PS.…”

“…These works and findings were used as a proof of a unique applicability of Sentinel-1 InSAR analyses and were the base for establishing this nation-wide Sentinel-1 InSAR monitoring system first as Sentineloshka [15], with an improved version as IT4S1 [16] at the Czech national supercomputing center, IT4Innovations. The key improvement is in the use of a modified metadata database structures from a previous version of the LiCSAR system [17].…”