Strategy Used for Phase Unwrapping in the NSBAS MT-InSAR Chain

Unwrapping long temporal baseline interferograms in areas with abundant crop cover is essential to avoid phase bias in small baseline subset methods. The unwrapping method described here includes four steps, (1) flattening of wrapped interferograms, (2) noise reduction by multi-looking and filtering with quality assessment, (3) a region-growing quality-based unwrapping, (4) an iterative correction of unwrapping errors. We show the effectiveness of such a procedure on Sentinel-1 time series in NE France for generating time series on a 750km by 250km track.