GNSSInSAR

GNSSInSAR is the integrated use of Global Navigation Satellite System (GNSS) measurements and Interferometric Synthetic Aperture Radar (InSAR) data to monitor and analyze ground deformation. The approach combines the strengths of both techniques: GNSS provides precise point measurements of displacement in three dimensions with continuous time series, while InSAR offers dense spatial coverage of line-of-sight deformation over large areas.

InSAR measures surface movement by detecting phase changes between radar images, yielding high-resolution maps of line-of-sight displacement but typically with limited temporal sampling and sensitivity to atmospheric disturbances. GNSS supplies ground-trtruth displacement data at specific stations and can provide independent time series, including horizontal components. The combination enables more accurate, robust deformation monitoring and helps resolve ambiguities inherent in InSAR, such as decorrelation or atmospheric effects.

Common GNSSInSAR approaches include joint inversion or data fusion where InSAR LOS measurements are combined with GNSS 3D or time-series data to estimate full three-dimensional deformation fields, or to constrain InSAR-derived time series with GNSS information. GNSS-derived tropospheric delays and phase screens can also be used to improve atmospheric corrections in InSAR processing. The workflow typically involves acquiring synchronized GNSS and SAR data, processing InSAR to generate LOS displacement maps, extracting GNSS time series or 3D displacements, and performing a joint inversion or assimilation to produce a coherent deformation model.

Applications span seismology, volcanology, tectonics, landslide monitoring, and infrastructure deformation studies. Advantages include enhanced spatial and temporal resolution, improved calibration and validation of InSAR results, and more reliable separation of deformation signals from atmospheric and orbital noise. Limitations arise from GNSS station density, the need for careful co-registration, and residual atmospheric or ionospheric effects.