Study of Systematic Bias in Measuring Surface Deformation with SAR
Interferometry
Abstract
This paper investigates the presence of a new interferometric signal in
multilooked Synthetic Aperture Radar (SAR) interferograms which cannot
be attributed to atmospheric or earth surface topography changes. The
observed signal is short-lived and decays with temporal baseline;
however, it is distinct from the stochastic noise usually attributed to
temporal decorrelation. The presence of such fading signal introduces a
systematic phase component, particularly in short temporal baseline
interferograms. If unattended, it biases the estimation of Earth surface
deformation from SAR time series.
The contribution of the mentioned phase component is quantitatively
assessed. For short temporal baseline interferograms, we quantify the
phase contribution to be in the regime of 5 rad at C-band. The biasing
impact on deformation signal retrieval is further evaluated. As an
example, exploiting a subset of short temporal baseline interferograms
which connects each acquisition with the successive 5 in the time
series, a significant bias of -6.5 mm/yr is observed in the estimation
of deformation velocity from a four-year Sentinel-1 data stack. A
practical solution for mitigation of this physical fading signal is
further discussed; special attention is paid to the efficient processing
of Big Data from modern SAR missions such as Sentinel-1 and NISAR.
Adopting the proposed solution, the deformation bias is shown to
decrease to -0.24 mm/yr for the Sentinel-1 time series.
Based on these analyses, we put forward our recommendations for
efficient and accurate deformation signal retrieval from large stacks of
multilooked interferograms.