Integration of InSAR and GPS for precise deformation mapping

Transcription

1 Integration of InSAR and GPS for precise deformation mapping Zhenhong Li (COMET, University of Glasgow, UK) Eric J. Fielding (Jet Propulsion Laboratory, Caltech, USA) 30 November 2009 Contents Two major error sources for InSAR Atmospheric effects and orbital errors InSAR/GPS integrated techniques GPS Topography-dependent Turbulence Model (GTTM) GPS Constrained Baseline Refinement model (GCBR) Conclusions InSAR: Two major error sources

2 effects: simulated from MERIS Long-wavelength orbital errors (Brazil) (Brazil) Part Two InSAR/GPS integration: GPS Topography-dependent Turbulence Model (GTTM)

3 InSAR water vapour correction models Ground-based measurements (GPS) Wadge et al (UK) Xu et al (China) Jassen et al (Australia) Onn & Zebker (USA) Li et al (UK) Space-based water vapour measurements (MERIS, MODIS) Li et al (UK): 4 models Numerical Weather Models (UM, MM5): Wadge et al (UK) Foster et al (USA) Puysségur et al (France) GPS Topography-dependent Turbulence Model (GTTM) Underlying assumptions: variations conform temporally & spatially to a statistical turbulent model; distributions are correlated with topography to some extent. References: Li, Z., P. Cross, and J.P. Muller, Successful application of GPS-derived water vapor to the improvement of the estimation of surface deformation from InSAR, in ION GNSS 2005, pp. Session A-6, p , Long Beach, California, September 13-16, Li, Z., E.J. Fielding, P. Cross, and J.-P. Muller, Interferometric synthetic aperture radar atmospheric correction: GPS topography-dependent turbulence model, Journal of Geophysical Research, 111 (B2), B02404, GTTM correction Key features: ZPDDM from WGS84 to Radar Coordinate System Correction correction before filtering and phase unwrapping Standard interferometric processing Flowchart of GTTM

4 GTTM correction Signals Subsidence Signals RMS: 1.1 cm RMS: 0.6 cm Part Three InSAR/GPS integration: GPS Constrained Baseline Refinement (GCBR) Orbit errors Errors in Satellite Orbits c.5-7 cm (radial) + ~3 times bigger (across-track) Planar/quadratic error in interferogram Tibetan experiment: Envisat Common way: remove a best-fit plane/quadratic surface

5 Effects of removing a best-fit plane from deformation signals (Adapted from Biggs et al. [2007]) TOPO Baseline Refinement in ROI_PAC Data: Unwrapped phase Topography (DEM) Assumptions: No localized deformation No water vapour effects Resultant baseline: No physical meaning Remove longwavelenth signals, including water vapour, deformation, etc TOPO Baseline: physical meaning? (a) Precise Orbit (b) TOPO baseline (c) GTTM + TOPO Baseline Precise orbit Origin TOPO GTTM TOPO Horizontal (m) Vertical (m) Slightly closer NB: Accuracy of precise Envisat orbit: c.5-7 cm (radial) + ~3 times bigger (across-track)

6 GPS Constrained Baseline Refinement (GCBR) (,,,,,, _ ) λ ZPDD ϕ Δ ρ GPS = f bh b& h b&& h bv b& v b&& v phs const 4π cosθ Baseline Parameters: Horizontal/vertical baselines; baseline rates, baseline accelerations; and phase constant (7 in total) Inputs: Unwrapped phase GPS deformation GPS tropospheric delays GPS positions Resultant baseline: With physical meaning Separate orbit errors from long-wavelength signals (incl. water vapour and some deformation signals) GCBR + GTTM Correction Key features: Both atmospheric effects and orbit errors can be addressed Baseline Refinement Flowchart of GCBR + GTTM GTTM + GCBR (a) Origin + TOPO (b) GTTM +TOPO (c) GTTM + GCBR Subsidence Precise Origin SignalsGTTM GTTM Baseline orbit TOPO TOPO GCBR Signals Horizontal (m) Vertical (m) Slightly -- closer Uncertainty NB: Accuracy of precise Envisat orbit: due to TOPO? RMS: 1.1 cm c.5-7 cm (radial) RMS: ~3 times cm bigger (across-track) RMS: 0.6 cm

7 Conclusions GTTM can be used to reduce atmospheric effects significantly RMS decreased from 1.1 cm to 0.6 cm InSAR baselines can be PROPERLY refined using GCBR Two potential limiting factors: GPS network and baseline model Potential applications for the GTTM/GCBR integrated technique: Interseismic motion Postseismic movements Other long-wavelength land subsidence signals