InSAR datum connection using GNSS-augmented radar transponders

Deformation estimates from Interferometric SyntheticAperture Radar (InSAR) are relative: they form a ‘free’network referred to an arbitrary datum, e.g. by assuming a referencepoint in the image to be stable. However, some applicationsrequire ‘absolute’ InSAR estimates, i.e. expressed ina well-defined terrestrial reference frame, e.g. to compareInSAR results with those of other techniques. We propose amethodology based on collocated InSAR and Global NavigationSatellite System (GNSS) measurements, achieved byrigidly attaching phase-stable millimetre-precision compactactive radar transponders to GNSS antennas. We demonstratethis concept through a simulated example and practical casestudies in the NetherlandsMathematical Geodesy and PositioningPhysical and Space Geodes