InSAR Greece with Parallelized Persistent Scatterer Interferometry: A National Ground Motion Service for Big Copernicus Sentinel-1 Data

Abstract

Advances in synthetic aperture radar (SAR) interferometry have enabled the seamless monitoring of the Earth's crust deformation. The dense archive of the Sentinel-1 Copernicus mission provides unprecedented spatial and temporal coverage; however, time-series analysis of such big data volumes requires high computational efficiency. We present a parallelized-PSI (P-PSI), a novel, parallelized, and end-to-end processing chain for the fully automated assessment of line-of-sight ground velocities through persistent scatterer interferometry (PSI), tailored to scale to the vast multitemporal archive of Sentinel-1 data. P-PSI is designed to transparently access different and complementary Sentinel-1 repositories, and download the appropriate datasets for PSI. To make it efficient for large-scale applications, we re-engineered and parallelized interferogram creation and multitemporal interferometric processing, and introduced distributed implementations to best use computing cores and provide resourceful storage management. We propose a new algorithm to further enhance the processing efficiency, which establishes a non-uniform patch grid considering land use, based on the expected number of persistent scatterers. P-PSI achieves an overall speed-up by a factor of five for a full Sentinel-1 frame for processing in a 20-core server. The processing chain is tested on a large-scale project to calculate and monitor deformation patterns over the entire extent of the Greek territory—our own Interferometric SAR (InSAR) Greece project. Time-series InSAR analysis was performed on volumes of about 12 TB input data corresponding to more than 760 Single Look Complex Sentinel-1A and B images mostly covering mainland Greece in the period of 2015–2019. InSAR Greece provides detailed ground motion information on more than 12 million distinct locations, providing completely new insights into the impact of geophysical and anthropogenic activities at this geographic scale. This new information is critical to enhancing our understanding of the underlying mechanisms, providing valuable input into risk assessment models. We showcase this through the identification of various characteristic geohazard locations in Greece and discuss their criticality. The selected geohazard locations, among a thousand, cover a wide range of catastrophic events including landslides, land subsidence, and structural failures of various scales, ranging from a few hundredths of square meters up to the basin scale. The study enriches the large catalog of geophysical related phenomena maintained by the GeObservatory portal of the Center of Earth Observation Research and Satellite Remote Sensing BEYOND of the National Observatory of Athens for the opening of new knowledge to the wider scientific community.

Integrated Analysis of the Combined Risk of Ground Subsidence, Sea Level Rise, and Natural Hazards in Coastal and Delta River Regions

“…Moreover, studies on overpopulation, human mass movements, the effects of epidemics on the Earth environment, and the interrelations between the different sources of environmental changes are expected to increase in number and relevance in the following years. In this context, the SAR technology and the differential SAR interferometry methods, which have been developed over almost the last 25 years, are expected to evolve in new directions to extract new pieces of information that are still hidden both in single radar microwave image and large sequences of data (the big data paradigm) (see for instance [78,79]). (v) Enhancing the knowledge of tidal evolution and sea level rise patterns and mechanisms in coastal zones, especially in delta regions of interest, through the utilization of next-generation satellite altimeters such as the recently launched Sentinel-6 platform and the Chinese Haiyang (HY) instrument series.…”

Characterizing land deformations in Western Greece with satellite remote sensing observations and in situ ground monitoring

“…A widely used methodology for the spatiotemporal monitoring of land displacements is based on Interferometric Synthetic Aperture Radar (InSAR) techniques. Such applications are possible via openly availably microwave satellite remote sensing data (e.g., Sentinel-1 [4], [5], [6], [7], ENVISAT SAR [8], [9] etc.). The processing of the collected observations is typically done with the Persistent Scatterer Interferometry (PSI) technique, with its implementation in the Stanford Method for Persistent Scatterer (StaMPS) being widely used.…”

Evaluation of Pixel Selection Methods for Traffic Infrastructure Monitoring Using Sentinel-1 Insar

“…The suitability of InSAR for monitoring task was shown by region-wide (Del Soldato et al, 2019), nation-wide (Kalia et al, 2017;Dehls et al, 2019;Papoutsis et al, 2020;Bakon et al, 2020;Bischoff et al, 2020) and european-wide (Crosetto et al, 2020) ground motion services. Country and continental-scale ground motion services deliver valuable information, but the In-SAR processing chain in such services is not optimized for specific tasks such as traffic infrastructure monitoring Motagh, 2017, 2021).…”