Methods to avoid being affected by non-zero closure phase in InSAR time series analysis in a multi-reference stack
U. Wegmüller, Christophe Magnard, Charles Werner, Tazio Strozzi, Rafael Caduff, Andrea Manconi
Abstract
This work discusses InSAR time series analysis using multi-reference stacks with exclusively short time intervals. A 5 months long stack of Sentinel-1 acquisitions over a high alpine territory that includes fast moving landslides is used. Use of the multi-look phases becomes problematic due to non-zero closure phase. The errors induced by non-zero phase closure can be avoided by the use of single-look phases for all scatterers, including distributed scatterers. A weighted least-squares solution of the deformation time-series is obtained using the multi-reference stack interferometric single-look phases. Quality control is done during the regression analysis, the conversion to the time series, and considering the temporal coherence. Spatial filtering of the single-look phase time series can be used to further reduce the phase noise present in areas with intermediate coherence levels.