On the Phase Nonclosure of Multilook SAR Interferogram Triplets

Abstract

This work explores the properties characterizing the phase non-closure of multi-look synthetic aperture radar (SAR) interferograms. Specifically, we study the implications of multi-look phase time incongruences on the generation of ground displacement time-series through small baseline (SB) multi-temporal InSAR (Mt-InSAR) methods. Our research clarifies how these phase inconsistencies can propagate through a time-redundant network of SB interferograms and contribute, along with phase unwrapping (PhU) errors, to the quality of the generated ground displacement products. Moreover, we analyze the effects of short-lived phase bias signals that could happen in sequences of short baseline (SB) interferograms and propose a strategy for their mitigation. The developed methods have been tested using both simulated and real SAR data. The latter were collected by the Sentinel-1A/B (C-band) sensors over the study areas of Nevada state, U.S., and Sicily Island, Italy.

Fine-Resolution Measurement of Soil Moisture From Cumulative InSAR Closure Phase

“…Such errors are usually small compared to the atmospheric noise component in an individual interferogram; however, when computing a time series, it is possible for the bias to compound and become quite large [15]. Some works characterize or correct this bias, including methods outlined in [15], [18], [19], [38], [39], [43]- [45]; many of these take advantage of the full stack of interferograms or of longer temporal baselines, which empirically observe lower systematic phase biases [15]. Others invert for soil moisture explicitly [14], [16], [20], [46], using models of varying complexity.…”

Sequential DS-ISBAS InSAR Deformation Parameter Dynamic Estimation and Quality Evaluation

“…Multi-look SB interferograms have bias [47][48][49][50]. Redundant interferograms can facilitate the identification and correction of the phase inconsistency and bias.…”

Post-Event Surface Deformation of the 2018 Baige Landslide Revealed by Ground-Based and Spaceborne Radar Observations

“…A common strategy to minimize coherence loss is to use interferograms with short time baselines. However, it has recently been shown that using this strategy can introduce a bias [29][30][31]. Although the bias caused by such inconsistencies is small in each individual interferogram, its accumulation in time could impact the final estimated velocities [32].…”