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Torsten Mayer-Gürr, Annette Eicker, Judith Schall

Regional high resolution geoid and mean sea surface topography determination by a combination of GOCE, GRACE and altimetry data. Torsten Mayer-Gürr, Annette Eicker, Judith Schall Institute of Geodesy and Geoinformation University of Bonn. Overview. ITG- Goce : Global GOCE SGG only solution.

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Torsten Mayer-Gürr, Annette Eicker, Judith Schall

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  1. Regional high resolution geoid and mean sea surface topography determination by a combination of GOCE, GRACE and altimetry data Torsten Mayer-Gürr, Annette Eicker, Judith Schall Institute of Geodesy and GeoinformationUniversity of Bonn

  2. Overview ITG-Goce: Global GOCE SGG onlysolution Regional gravityfieldrefinement GRACE + GOCE Regional gravityfieldrefinement GRACE + GOCE + Altimetry

  3. GOCE data ITG-Goce (preliminaryresults) 1 monthofdata: - gradiometerdata - starcameradata - orbitdata Computedwiththeshortarcmethod: Foreachshortarc (15 min) - fullvariancecovariance - biasparameterforeach SGG component - SST contributionismissingyet

  4. Median degree variances signal formal errors

  5. Median degree variances signal formal errors Difference ITG-Goce – EIGEN-05c

  6. Median degree variances signal formal errors Difference ITG-Goce – EIGEN-05c Difference ITG-Goce – ITG-Grace2010s

  7. Regional gravity field recovery GRACE GOCE Regional refinement Global reference solution Spherical harmonics Spherical splines

  8. ITG-Grace2010s gravity anomalies

  9. ITG-Grace2010s gravity anomalies

  10. Representation of geoid heights The residual gravityfieldrepresentedby a linear combinationoflocalizingbasisfunctions HarmonicSplines shapecoefficients(expectedspectralcontent)

  11. Observation equations Observation equations GOCE GRACE field normal equations Thisapproachhassimilaritiesto: • regularization • combinationwithspectralweighting • least squarescollocation For the descripition of the theory see Eicker(2006)

  12. Results – gravity anomalies ITG-Grace2010s +

  13. Regional gravity field recovery GRACE GOCE Regional refinement Global reference solution Spherical harmonics Spherical splines

  14. Regional gravity field recovery GRACE GOCE Altimetry T/P, ERS 1/2, ... Regional refinement Global reference solution Spherical harmonics Spherical splines

  15. MDT Sea surface SSH Geoid Geoid height Ellipsoid Altimetry Altimetrydata(T/P, ERS 1/2, …) Altimetrycanimprovetheresolutionofthe GRACE/GOCE geoid. But: Altimeter satellitesmeasurestheseasurfaceheight (SSH) and not thegeoidheight => Combinedestimationofgeoidand MDT

  16. MDT Sea surface SSH Geoid Geoid height Ellipsoid Altimetry Altimetrydata(T/P, ERS 1/2, …) Observation equation meansea surfaceheight mean dynamictopography geoidheight = + Localizingbasisfunctionsadaptedtothespectralcontenentofthe MDT Localizingbasisfunctionsadaptedtothespectralcontenentofthe residual gravityfield

  17. Observation equations Complete observation equations Altimetry GOCE GRACE field apriori (stochastical)information from MDT gravity MDT Relative weighting of each set of observations by thevariance component estimation method (VCE)(Koch & Kusche 2001)

  18. Results – gravity anomalies + + +

  19. Results – mean dynamic topography

  20. Results – gravity anomalies + + +

  21. Results – gravity anomalies + +

  22. Results – gravity anomalies EGM2008 + +

  23. Results – gravity anomalies Differences(RMS 8 mGal) EGM2008 + +

  24. Summary GOCE improves the gravity fieldcompared to GRACE in the high degrees Our first GOCE solution (ITG-Goce) fits better toITG-Grace2010s than to EIGEN-05Cin the medium degrees (n=90…150) Refinenemtof GRACE + GOCE gravityfield withAltimetry (T/P, ERS 1/2, ...)leadsto: • Regional highresolution Geoid • Estimationofthemeandynamictopography (MDT) Geoid Topography

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