On Closure Phase and Systematic Bias in Multi-looked SAR Interferometry


In this article, we investigate the link between closure phase and the observed systematic bias in deformation modeling with multi-looked SAR interferometry. Multi-looking or spatial averaging is commonly used to reduce stochastic noise over a neighborhood of distributed scatterers in InSAR measurements. However, multi-looking may break consistency among a triplet of interferometric phases formed from three acquisitions leading to a residual phase error called closure phase. Understanding the cause of closure phase in multi-looked InSAR measurements and the impact of closure phase errors on the performance of InSAR time-series algorithms is crucial for quantifying the uncertainty of ground displacement time-series derived from InSAR measurements. We develop a model that consistently explains both closure phase and systematic bias in multi-looked interferometric measurements. We show that non-zero closure phase can be an indicator of temporally inconsistent physical processes that alter both phase and amplitude of interferometric measurements. We propose a method to estimate the systematic bias in the InSAR time-series with generalized closure phase measurements. We validate our model with a case study in Barstow-Bristol trough, California. We find systematic differences on the order of cm/year between InSAR time-series results using subsets of varying maximum temporal baseline. We show that these biases can be identified and accounted for.

IEEE Transactions on Geoscience and Remote Sensing
Yujie Zheng
Yujie Zheng
Postdoctoral scholar

My research focuses on developing and applying new techniques to analyze a combination of geodetic observations to better understanding changes of the Earth’s surface related to natural and anthropogenic processes.