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Supplementary information Analytical Techniques and Measurement Uncertainty

Summary: Supplementary information
Analytical Techniques and Measurement Uncertainty
Interferomeric SAR (InSAR) allows measurement of millimetre-level surface
displacements, including land subsidence, in the radar illumination direction1-10
. This is
accomplished by phase comparison of two or more images separated in time. Apart from
cycle ambiguity problems, the main limitations are related to temporal and geometrical
decorrelation (low signal to noise ratio in the phase change estimate), and variable
tropospheric water vapor, which can generate variable path delay for microwave signals
unrelated to surface motions. In sub-tropical and tropical regions, the tropospheric delay
may be as high as 10 cm over several weeks 11-12
. This constitutes a significant potential
error source for InSAR, and has tended to restrict most InSAR studies to relatively dry
regions. Permanent Scatterer InSAR (PSInSAR)13-18
exploits several characteristics of
radar scattering and atmospheric decorrelation to measure surface displacement in
otherwise non-optimum conditions, including humid regions. Atmospheric phase
contributions are spatially correlated within a single SAR scene, but are generally
uncorrelated in time. Conversely, target motion is usually strongly correlated in time.
Thus, atmospheric effects can be estimated and removed by combining data from long time


Source: Amelung, Falk - Rosenstiel School of Marine and Atmospheric Sciences, University of Miami
Miami, University of - Geodesy Laboratory


Collections: Geosciences