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TRANSITION OF THE IGS REFERENCE FRAME COORDINATION FROM NRCAN TO IGN - STATUS AND PROSPECTS

TRANSITION OF THE IGS REFERENCE FRAME COORDINATION FROM NRCAN TO IGN - STATUS AND PROSPECTS. Tasks of the RF Coordinator. Operational tasks: Weekly combination of the AC SINEX (Stations coordinates, ERP, apparent geocenter)

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TRANSITION OF THE IGS REFERENCE FRAME COORDINATION FROM NRCAN TO IGN - STATUS AND PROSPECTS

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  1. TRANSITION OF THE IGSREFERENCE FRAME COORDINATIONFROM NRCAN TO IGN- STATUS AND PROSPECTS 35th IGS Governing Board Meeting December 13, 2009 – San Francisco

  2. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Tasks of the RF Coordinator • Operational tasks: • Weekly combination of the AC SINEX (Stations coordinates, ERP, apparent geocenter) • Accumulation of the weekly combined solutions(Stations coordinates and velocities) • Detection of stations discontinuities • Occasional tasks: • Provide official IGS submissions to the ITRF • Issue official IGS RF realizations • Provide satellite antenna offsets • Combine and accumulate AC reprocessed solutions operational automation to be done

  3. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Weekly combination: NRCAN strategy • Preprocessing of AC solutions: • Unconstraining • Augmentation with explicit geocenter parameters • Alignment to IGS05 • Detection and removal of outliers • Iterative combinations:(weighted stacking of normal equations) • AC variance factors = (WRMS of the “AC vs. cumulative” comparison)² • No transformation parameters estimated • No detection of outliers • Until: convergence of the variance factors

  4. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Weekly combination: IGN strategy • Preprocessing of AC solutions: • Unconstraining • Detection and removal of outliers • Iterative combinations: • AC variance factors: degree of freedom estimator • “AC ↔ combined” transformation parameters estimated • Detection of outliers • Until: No outliers + 1 iteration • Last combination: • Augmentation of the AC solutions with explicit geocenter parameters • Transformation parameters fixed • The combined solution is finally rescaled and aligned to IGS05.

  5. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco AC variance factors • NRCAN: : residuals of the “AC ↔ cumulative” comp. : number of common stations : normal matrix of AC solution • IGN: : redundancy factor : AC residuals from the combination : number of observations from this AC : design matrix for this AC : combined covariance matrix (*) The IGN combined solution is finally rescaled. For week 1558, SF = (2.941) ²

  6. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Transformation parameters • NRCAN: • No transformation parameters are estimated since all AC solutions are aligned to IGS05.(⇒ They are supposed to be in the same frame.) • But the set of reference stations is different for each AC… • IGN: • Each AC solution is in its own frame. • Alignment to IGS05 is made at the level of the combined solution.

  7. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: Stations coordinates • Agreement at: • 0.3-0.4 mm in N, E • ~ 1 mm in Up • Accidents: • Week 1505: YKRO • Week 1514: CONT • Week 1519: STR1 • Week 1531: SAMP • Week 1552: BAKO • Week 1555: KATZ

  8. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: Helmert parameters • All below 1 mm • And there is an explanation! • Sets of reference stations are not the same because of: • Solution numbers • Outliers • Green lines: TIGN / IGS05-NRCAN- TNRCAN / IGS05-IGN

  9. IGN vs. NRCAN: ERP • Differences are globallybelow the level of uncertainty • XPOR, YPOR: SIO estimates are included in IGN solutions • XPOR, YPOR, LOD: part of the differences can be explained by the different AC weightings 35th IGS Governing Board Meeting December 13, 2009 – San Francisco

  10. IGN vs. NRCAN: Geocenter • Differences sometimes higher than the level of uncertainty(1.5 mm, 1.3 mm, 3.0 mm) • GFZ geocenter is included in the IGN solutions. • Influence of AC weightings 35th IGS Governing Board Meeting December 13, 2009 – San Francisco

  11. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Metadata • NRCAN: • From igs.snx for IGS stations • From AC solutions for other stations • IGN: • Sites logs are gathered from several sources.(IGS, EPN, CORS, UNAVCO…) • Metadata are extracted from the sites logs. • Week 1558: Sites logs were available for 396 stations over 408.

  12. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Cumulative solution • NRCAN strategy was reproduced: • Addition of a loosely constrained weekly solutionto a loosely constrained cumulative solution(No transformation parameters are estimated.) • Rejection of stations without domes or with poor velocity estimates • Addition of internal constraints • Start point is IGS09P45_all.snx.(cumulative solution for week 1557)

  13. IGN09P46.snx vs. IGS09P46.snx Helmert parameters: WRMS : Differences are all (far) below the uncertainties. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco

  14. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Discontinuities • Currently, there is no discontinuity catalogue compatible with the IGS cumulative solution. (ALL.snx was modified according to the repro1 results.) • This catalogue was built from ALL.snx and older versions. • A SOLUTION/DISCONTINUITY block will be included in each IGN cumulative solution.

  15. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Plans • January 2010: Test of orbits/clocks combination using IGN products • February 2010: IGN becomes the operational RF coordinator. • Early 2010: • IGS08 (subset of ITRF2008?) • Backsolve repro1 to derive satellite offsets consistent with IGS08 • IGN combination of repro1? • Later: • Replacement of the operational cumulative solution by a solution based on repro1 (NRCAN? or IGN?) • Website devoted to IGS RF

  16. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco THANKS FOR YOUR ATTENTION

  17. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: AC geocenters

  18. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: AC geocenters STD

  19. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGS05

  20. 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Reference stations left on week 1558

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