Enhancement: Coherence as a proxy for phase noise

[mcgarth]

Use coherence maps to derive a pixel by pixel phase noise proxy statistic for each pixel in each interferogram. Use this proxy as a criteria for picking the Minimum Spanning Tree of interferograms. Also add the phase noise to the variance covariance matrix for weighting interferograms in time series inversion (see Gonzalez & Fernandez JGR 2011)

[sheecegardezi]

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2011JB008412