1/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco TRANSITION OF THE IGS REFERENCE FRAME COORDINATION FROM NRCAN TO IGN - STATUS AND PROSPECTS

2/16 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

3/16 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

4/16 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.

5/16 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 Example: VF comparison for week 1558 AC NRCAN √VF IGN √VF x2.941 ( * ) Ratio COD EMR ESA GFZ JPL MIT NGS SIO (*) The IGN combined solution is finally rescaled. For week 1558, SF = (2.941) ²

6/16 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.

7/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: Stations coordinates Agreement at: – 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

8/16 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: T IGN / IGS05-NRCAN -T NRCAN / IGS05-IGN

9/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: ERP dXPO (µas) dYPO (µas) dXPOR (µas/d) dYPOR (µas/d) dLOD (µs) Mean Abs.max Std Differences are globally below 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

10/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: Geocenter dXGC (mm) dYGC (mm) dZGC (mm) Mean Abs.max Std 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

11/16 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.

12/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Cumulative solution NRCAN strategy was reproduced: –Addition of a loosely constrained weekly solution to 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)

13/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN09P46.snx vs. IGS09P46.snx TX (mm) TY (mm) TZ (mm) SCL (ppb) RX (mas) RY (mas) RZ (mas) dTX / dt (mm/y) dTY / dt (mm/y) dTZ / dt (mm/y) dSCL / dt (ppb/y) dRX / dt (mas/y) dRY / dt (mas/y) dRZ / dt (mas/y) Helmert parameters: WRMS : Differences are all (far) below the uncertainties. N (mm) E (mm) U (mm) VN (mm/y) VE (mm/y) VU (mm/y)

14/16 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.

15/16 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

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

17/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: AC geocenters

18/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGN vs. NRCAN: AC geocenters STD

19/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco IGS05

20/16 35th IGS Governing Board Meeting December 13, 2009 – San Francisco Reference stations left on week 1558