Interferometric Synthetic Aperture Radar (InSAR) is a family of techniques for processing satellite radar imagery in order to measure ground displacements. It can offer significant spatial coverage (orders of 1000 km2 constrained only by processing time) thus potentially providing significant advantages (cost, time, coverage and accuracy) over more traditional techniques such as levelling and GPS.
InSAR is now widely used to characterize natural hazards such as earthquakes and volcanic eruptions, as well as human induced changes such as mine subsidence and aquifer drawdown. It is now possible to distinguish, for example, geological fault driven movement from aquifer recharge by separating both horizontal and vertical ground movements.
With nearly three decades of data, Persistent Scatterer Interferometry (PSI) is able to achieve sub-millimetre precision in displacement; analysis of long time-series data as part of the site investigation desk study can identify unusual patterns of displacement from past land use, e.g. cemeteries and historic landfill, and natural hazards such as faults and buried hollows.
However, analysis of InSAR and PSI data requires care and experience to identify causes of anomalies and eliminate artefacts.
Image based on data from TRE-ALTAMiRA.
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