Abstract
The growing volume of synthetic aperture radar (SAR) imagery acquired by satellite constellations creates novel opportunities and opens new challenges for interferometric SAR (InSAR) applications to observe Earth’s surface processes and geohazards. In this paper, the Parallel Small BAseline Subset (P-SBAS) advanced InSAR processing chain running on the Geohazards Exploitation Platform (GEP) is trialed to process two unprecedentedly big stacks of Copernicus Sentinel-1 C-band SAR images acquired in 2014–2020 over a coastal study area in southern Italy, including 296 and 283 scenes in ascending and descending mode, respectively. Each stack was processed in the GEP in less than 3 days, from input SAR data retrieval via repositories, up to generation of the output P-SBAS datasets of coherent targets and their displacement histories. Use-cases of long-term monitoring of land subsidence at the Capo Colonna promontory (up −2.3 cm/year vertical and −1.0 cm/year east–west rate), slow-moving landslides and erosion landforms, and deformation at modern coastal protection infrastructure in the city of Crotone are used to: (i) showcase the type and precision of deformation products outputting from P-SBAS processing of big data, and the derivable key information to support value-adding and geological interpretation; and (ii) discuss potential and challenges of big data processing using cloud/grid infrastructure.
Highlights
The last three decades have witnessed the increasing and widespread use of satellite synthetic aperture radar (SAR) imagery to retrieve key information on surface deformation processes affecting the Earth’s surface using two- and three-pass differential interferometric SAR (InSAR) (e.g., [1,2,3]), and multi-pass/multi-temporal InSAR methods, such as persistent scatterers interferometry (PSI) (e.g., [4,5]) and Small BAseline Subset (SBAS)(e.g., [6,7])
Our experiment proves that nowadays, with the Geohazards Exploitation Platform (GEP) it is possible to process a whole time series of 300 Sentinel-1 SAR images at full swath in less than three days, without the necessity for in-house high-performance computers and data-storage capacity
Six full years of Sentinel-1 SAR ascending and descending mode imagery were processed with the Parallel Small BAseline Subset (P-SBAS) service available in European Space Agency (ESA)’s GEP to generate the longest ever interferometric stacks so far used for a single study site and published in the specialist SAR
Summary
The last three decades have witnessed the increasing and widespread use of satellite synthetic aperture radar (SAR) imagery to retrieve key information on surface deformation processes affecting the Earth’s surface using two- and three-pass differential interferometric SAR (InSAR) (e.g., [1,2,3]), and multi-pass/multi-temporal InSAR methods, such as persistent scatterers interferometry (PSI) (e.g., [4,5]) and Small BAseline Subset (SBAS)(e.g., [6,7]). Many SAR constellations have been developed since the 1990s and, as part of their background observation scenarios, have been tasked to acquire images regularly over major cities, targets with economic and/or strategic relevance (e.g., key infrastructure, polar regions, cultural heritage sites), regions affected by specific Earth hazards (e.g., tectonic zones and volcanoes), and entire nations or continents (e.g., [8,9]) This means that the volume of SAR data collected to date, archived, and available for InSAR applications by far falls within the “big data” remit for such type of imagery (typically, 15–20 SAR scenes are needed as minimum input of an advanced InSAR analysis, e.g., [5], and usually a few to several tens of scenes are used in most InSAR applications), creating novel opportunities and opening new challenges for Earth sciences and observation (e.g., [10,11]). Researchers willing to undertake multi-temporal InSAR studies of long-term (e.g., more than 3–5 years) dynamics of deformation processes face two main challenges
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