Baseline Subset Interferometric Synthetic Aperture Research Articles

Removal of systematic seasonal atmospheric signal from interferometric synthetic aperture radar ground deformation time series

AbstractApplying the Multidimensional Small Baseline Subset interferometric synthetic aperture radar algorithm to about 1500 Envisat and RADARSAT‐2 interferograms spanning 2003–2013, we computed time series of ground deformation over Naples Bay Area in Italy. Two active volcanoes, Vesuvius and Campi Flegrei, are located in this area in close proximity to the densely populated city of Naples. For the first time, and with remarkable clarity, we observed decade‐long elevation‐dependent seasonal oscillations of the vertical displacement component with a peak‐to‐peak amplitude of up to 3.0 cm, substantially larger than the long‐term deformation rate (<0.6 cm/yr). Analysis, utilizing surface weather and radiosonde data, linked observed oscillations with seasonal fluctuations of water vapor, air pressure, and temperature in the lower troposphere. The modeled correction is in a good agreement with observed results. The mean, absolute, and RMS differences are 0.014 cm, 0.073 cm, and 0.087 cm, respectively. Atmospherically corrected time series confirmed continuing subsidence at Vesuvius previously observed by geodetic techniques.

Time-series analysis of subsidence associated with rapid urbanization in Shanghai, China measured with SBAS InSAR method

River delta plains (deltas) are susceptible to subsidence producing undesirable environmental impact and affecting dense population. The City of Shanghai, located in the easternmost of Yangtze Delta in China, is one of the most developed regions in China that experiences the greatest land subsidence. Excessive groundwater withdrawal is thought to be the primary cause of the land subsidence, but rapid urbanization and economic development, mass construction of skyscrapers, metro lines and highways are also contributing factors. In this paper, a spatial–temporal analysis of the land subsidence in Shanghai was performed with the help of the Small Baseline Subset Interferometric Synthetic Aperture Radar. Twenty l-band ALOS PALSAR images acquired during 2007–2010 were used to produce a linear deformation rate map and to derive time series of ground deformation. The results show homogeneous subsidence within the research area, but exceptionally rapid subsidence around skyscrapers, along metro lines, elevated roads and highways was also observed. Because groundwater exploitation and rapid urbanization responsible for much of the subsidence in the Shanghai region are expected to continue, future subsidence monitoring is warranted.

Simulation of time-series surface deformation to validate a multi-interferogram InSAR processing technique

A refined, small baseline subset (SBAS) interferometric synthetic aperture (InSAR) method has been developed to estimate time-series surface deformation through fusion of multi-interferogram processing. Using a synthetic data set that takes into account two time-varying deformation sources, topography-induced errors, atmospheric delay anomalies, orbital errors and temporal decorrelation, all of which are based on realistic ERS-1/ERS-2 SAR image acquisition dates and baseline configuration over the Seguam volcano, Alaska, we assess the accuracy of the refined SBAS technique. Detailed comparison between SBAS-derived products, including time-series deformation maps, atmospheric delays and baseline errors with those of synthetic values, attest the robustness of the refined SBAS technique. The root mean square error of the mean deformation rate between the simulated and SBAS-retrieved is about 0.66 mm year–1. Thus, the measurement accuracy of the refined SBAS method would be around 1 mm year–1.