Evaluating the Deformation Measurement Accuracy Using Low-SNR Radars for Future InSAR Missions

TL;DR

This paper investigates how low-SNR conditions affect the accuracy of deformation measurements in InSAR, demonstrating that with proper processing, reliable displacement data can be obtained even in challenging low-SNR environments, informing future SAR mission designs.

Contribution

The study quantifies the impact of low-SNR on InSAR displacement accuracy and proposes multilooking techniques to mitigate noise effects, enabling cost-effective future SAR missions.

Findings

Displacement accuracy of 4mm is achievable at SNR around -9dB to -10dB.

Multilooking improves coherence and reduces bias in low-SNR conditions.

Low-SNR systems can attain comparable velocity precision to high-SNR systems with appropriate processing.

Abstract

Interferometric Synthetic Aperture Radar (InSAR) is a powerful tool for monitoring surface deformation with high precision. However, low Signal-to-Noise Ratio (SNR) conditions, common in regions with low backscatter, can degrade phase coherence and compromise displacement accuracy. In this study, we quantify the impact of low-SNR conditions on InSAR-derived displacement using L-band UAVSAR data collected over the San Andreas Fault and Greenland ice sheet. We simulate low-SNR conditions by degrading the Noise-Equivalent Sigma Zero (NESZ) to $-15~\mathrm{dB}$ and assess the resulting effects on interferometric coherence, phase unwrapping, and time series inversion. The displacement accuracy of 4mm in single interferogram can be achieved by taking looks for the signal decorrelation of 0.6 and SNR between -9dB to -10dB. Our findings indicate that even under low-SNR conditions, a velocity precision of $0.5~\mathrm{cm/yr}$ can be achieved in comparison to high-SNR conditions. By applying multilooking with an 8x8 window, we significantly improve coherence and eliminate this bias, demonstrating that low-SNR systems can achieve comparable precision to high-SNR systems at the expense of spatial resolution. These results have important implications for the design of future cost-effective SAR missions, such as Surface Deformation and Change (SDC), and the optimization of InSAR processing techniques in challenging environments.