Integrating EGMS InSAR and GNSS for 3D Surface Deformation Monitoring: Reservoir-Driven Ground Motion in Groningen

Three-dimensional ground-motion products help interpret deformation sources and support decisions in deforming regions. GNSS provides high-precision 3D displacement at station locations. InSAR adds dense spatial coverage, but it measures motion mainly along the satellite line of sight (LOS) and has lower temporal resolution and higher latency. We combine GNSS with EGMS InSAR time series to obtain consistent 3D surface deformation over Groningen (the Netherlands), where decades of gas production have produced subsidence.
GNSS PPP daily positions from Nevada Geodetic Laboratory are cleaned for network-wide common-mode signals, corrected for long-period trends, and then expressed in a local reference frame tied to a central station. EGMS “Basic” InSAR time series are updated using smooth calibration behavior derived from the corresponding “Calibrated” products. We align the InSAR and GNSS references by removing the mean LOS deformation near the reference GNSS antenna at matched epochs. For the integration, we pair GNSS stations with nearby persistent scatterers and synchronize the time series. The datasets are fused with an uncertainty-aware least-squares approach to estimate 3D displacement in the East–North–Up (ENU) frame. In this work, we explore spatio-temporal extensions, such as Kalman filtering, and multi-geometry InSAR integration (ascending and descending orbits) to improve continuity and reduce directional bias. Spatially continuous deformation products are generated from the fused 3D estimates using interpolation techniques.
The outcome is a set of 3D deformation time series and maps that merge the spatial coverage of EGMS with the full-component information provided by GNSS. In Groningen, the integration reduces LOS-driven ambiguity, producing 3D deformation products that are easier to interpret across sensors. The workflow is designed as a practical monitoring deliverable and a reproducible basis for site-specific analysis. These outputs can serve as monitoring deliverables and as observational constraints to support site-specific interpretation of coupled reservoir-deformation models used in geo-energy settings.