Abstract
In this work, ground deformation of the Shanghai coastal area is inferred by using the multiple-satellite Differential Synthetic Aperture Radar interferometry (DInSAR) approach, also known as the minimum acceleration (MinA) combination algorithm. The MinA technique allows discrimination and time-evolution monitoring of the inherent two-dimensional components (i.e., with respect to east-west and up-down directions) of the ongoing deformation processes. It represents an effective post-processing tool that allows an easy combination of preliminarily-retrieved multiple-satellite Line-Of-Sight-projected displacement time-series, obtained by using one (or more) of the currently available multi-pass DInSAR toolboxes. Specifically, in our work, the well-known small baseline subset (SBAS) algorithm has been exploited to recover LOS deformation time-series from two sets of Synthetic Aperture Radar (SAR) data relevant to the coast of Shanghai, collected from 2014 to 2017 by the COSMO-SkyMed (CSK) and the Sentinel-1A (S1-A) sensors. The achieved results evidence that the Shanghai ocean-reclaimed areas were still subject to residual deformations in 2016, with maximum subsidence rates of about 30 mm/year. Moreover, the investigation has revealed that the detected deformations are predominantly vertical, whereas the east-west deformations are less significant.
Highlights
Differential interferometric synthetic aperture radar (DInSAR) [1,2,3] plays a significant role for the monitoring of Earth’s surface ground deformation, being able to retrieve accurate and timely information on the sensor’s line-of-sight-projected components of the terrain displacements
Differential interferograms were generated by computing the phase difference between the co-registered Synthetic Aperture Radar (SAR) image pairs, and by subtracting the relevant topographic phase contributions, as synthesized using the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM (30 × 30 m) of the area, for the CSK and the S1-A SAR datasets, respectively
The multi-angle/multi-sensor Differential Synthetic Aperture Radar interferometry (DInSAR) approach, known as Minimum Acceleration (MinA) combination and based on the joint exploitation of LOS-projected deformation time-series obtained by applying the small baseline subset (SBAS) technique [6], has been used
Summary
Differential interferometric synthetic aperture radar (DInSAR) [1,2,3] plays a significant role for the monitoring of Earth’s surface ground deformation, being able to retrieve accurate and timely information on the sensor’s line-of-sight-projected components of the terrain displacements. In order to partially circumvent the limitations due to the scarcity of high-stable PSs in ocean-reclaimed lands, small baseline approaches, which are able to investigate the deformation of distributed scatterers (DS) on the ground, have been applied [29,33] These latter investigations relied on the joint use of DInSAR-derived deformation measurements, derived by processing long-lasting sequences of ENVISAT and COSMO-SkyMed differential SAR interferograms, and empirical geotechnical models [29,33,34,35,36]. The LOS deformation time-series of the Shanghai coastal area, recovered by applying the small baseline subset (SBAS) algorithm to the two sets of COSMO-SkyMed (descending passages) and Sentinel-1A (ascending passages) data, have been combined to retrieve the up-down and the east-west components of deformation from 26 February 2015 to 4 March 2016 To this aim, the MinA technique [19] is applied. The presented results demonstrate the ocean-reclaimed land is subject to prevalent up-down movements (with a maximum subsidence rate of 30 mm/year), with the exception of some isolated areas, just in the proximity of the coastline, characterized by maximum lateral east-west deformation rates of 10 mm/year during the 2015–2016 observation period
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