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A pattern-based strategy for InSAR phase unwrapping and application to two 2 landslides in Colorado
  • Yusuf Eshqi Molan,
  • Rowena Lohman
Yusuf Eshqi Molan
Cornell University

Corresponding Author:[email protected]

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Rowena Lohman
Cornell University
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Abstract

Interferometric synthetic aperture radar (InSAR) has been successfully used to map ground displacements associate with landslides. One challenge with InSAR is that the basic measurement of interferometric phase takes values between 0 and 2π instead of values representing total displacement relative to some stable reference frame. Phase unwrapping is necessary to reconstruct measurements of total displacement for use in quantitative analysis. Unwrapping approaches often assume that the absolute phase difference between two neighboring pixels should be a small fraction of a cycle (π or less). In the presence of noise or high strain rates associated with fast-moving landslides, aliasing of the phase (under-sampling of the wrapped signal) can result in unwrapping errors and under- or overestimates of total displacement. Here we use a pattern-based strategy for phase unwrapping of InSAR observations of fast-moving landslides, where we determine the unwrapped deformation field that is most similar to a scaled reference displacement map. We also describe a range of metrics that we use to evaluate the most appropriate scaling for each interferogram and demonstrate the range of conditions where they perform well using synthetic data. For evaluation of the results, we generated UAVSAR wrapped interferograms over the Slumgullion landslide in Colorado where phase aliasing for interferograms with temporal baselines larger than seven days is common. We show the interferograms unwrapped with our approach and compare them against results from range offsets (pixel tracking), demonstrating that our approach can be used for time spans well beyond those where traditional phase unwrapping performs well.