Radar interferometry is a technique that combines the coherent phase from a pair of synthetic aperture radar (SAR) signals to provide three-dimensional information about the Earth’s surface. The technique requires the coregistration and processing of two SAR signals from very similar viewing geometries that have been acquired over the region of interest. By coherently combining the signals from the two acquisitions, the interferometric phase between the received signals can be determined for each imaged point.
The interferometric phase represents the difference in the path lengths to the imaged point. The interferometric phase is affected by topography, atmospheric effects, surface motion, and system noise. The effects of topography can be estimated and removed through the use of a (high-quality) digital elevation model (DEM) and knowledge of the radar characteristics (wavelength, range to target) and relative orbital positions (baseline length and drift).
After the effects of topographic, atmospheric and residual noise have been removed, the remaining phase differences are due to subsidence in the direction of the radar’s line of sight (LOS). If multiple data sets are available, a long term temporal assessment of motion can be created for each target.
The PCI algorithms that comprise InSAR can process both topographic and deformation information derived from multiple SAR sensors by using data sets ranging from a single interferometric pair to multiple stacks of single, dual, compact and fully polarimetric data to produce reliable and valuable map products.
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