Subject: [IGS-ACS-352] RE: [IGS-ACS-350] Re: ITRF2008P release for evaluation by Technique Centers From: Ferland, Rémi Date: Thu, 08 Apr 2010 13:59:19 -0400 To: jim.ray@noaa.gov, altamimi , igs-acs@igscb.jpl.nasa.gov ****************************************************************************** IGS-ACS Mail 08 Apr 10:59:32 PDT 2010 Message Number 352 ****************************************************************************** Dear Jim, Zuheir, et al. The following is a short summary to the contribution to the ITRF2008 that was provided at the end of July 2009. The contribution spans the period 1997.0 - 2009.5 (563 weeks) (GPS weeks 0886-1536) (1996/12/29 - 2009/07/04) The pre-2008 solutions are based on the reprocessed products, while the more recent solutions are based on the IGS official products. Minor improvements were made to the official products before resubmission. All weekly solution include weekly station coordinates and apparent geocenter position estimates as well as daily (at the middle of the day) pole position, pole rate, and LOD estimates. The weekly solutions also include full variance-covariance estimate. All weekly solutions are provided aligned to the IGS05 realization of ITRF2005. The ACs LOD parameters are calibrated w.r.t. Bulletin A. For detailed information on the reprocessing see: http://acc.igs.org/reprocess.html 1) Analysis strategy: ===================== The sequential procedures used to generate the official products and the reprocessed products are almost identical. They differ in: 1) The official sequential analysis runs forward in time, while the reprocessed runs backward. 2) The rejection criterion for the official products was set at 5 sigmas, while the reprocessed rejection was set an 8 sigmas. General strategy steps: - Rescale covariance information (from previous iteration) - Unconstrain - Consistency check / Outlier rejection between AC (& GNAAC) and: - Reference frame, - AC, - Previous week (weekly & cumulative) combined solutions, - Combine weekly solution, - Update cumulative solution. 2) ACs & GNAACs Contribution: ============================= 11 ACs and 2 GNAACs have contributed: AC data span Comments co[d1] 1997.0 - 2009.5 Excluded ERPs em[r1] 1997.0 - 2009.5 es[a1] 1997.0 - 2009.5 gf[z1] 1997.0 - 2009.5 Excluded apparent geocenter gt1 1998.2 - 2002.0 Excluded apparent geocenter jpl 2008.0 - 2009.5 mi[t1] 1998.0 - 2009.5 ng[s1] 1997.0 - 2009.5 pdr 1997.0 - 2008.0 Excluded ERPs si[o1] 1997.0 - 2009.5 Excluded pole rate ul1 1997.0 - 2007.0 Excluded apparent geocenter (no ERPs) GNAACs data span Comments MIT 2008.0 - 2009.5 Comparison only ncl 2008.0 - 2009.5 Comparison only 3) Combined Products: ===================== 560 stations with the following # of weekly solutions: Weeks From To # Stations 101 - 150 64 151 - 200 46 201 - 250 45 251 - 300 30 301 - 350 45 351 - 400 48 401 - 450 42 451 - 500 44 501 - 550 55 551 - 600 37 601 - 653 104 ---- Total 560 There is a total of 222261 positions estimates resulting in An average close to 395 stations estimates per weeks. Weekly *snx, *res, *sum, *res files are available at CDDIS. As per the original submisson in Feb 2009, the remarks concerning the statistics evolution: - The North weekly weighted average residuals w.r.t. the reference frame realization and the cumulative solution have an annual signal with amplitude of 1-2mm. - A similar annual signal can be seen in the estimated scale offset w.r.t. the reference frame. - The number of stations going back to 1997, is holding at above 175 every week. By comparison, when the original analysis was done for early 1997, there were ~95 stations in the weekly combinations. - The statistics of the residuals w.r.t. the reference frame are generally best in the weeks 1200-1400 (2003-2006) period. The increase after 1400 is most likely due to extrapolation of the reference frame and a decrease number of available stations; and before 1200 it is mostly due to a decrease of the number of available stations The AC horizontal/vertical consistency is still about (in mm) w.r.t.: IGS05 Combined Combined Weekly Cumulative 2-3 / 7-9 1-2 / 3-4 2-3 / 5-7 The overall ERP consistency of the ACs w.r.t. weekly combination is still about: LOD 15 us XPO 0.05 mas YPO 0.04 mas XPOR 0.14 mas/d YPOR 0.14 mas/d Thanks again for the ACs great effort, cooperation and patience, and all those (specially Jim Ray) that have provided ongoing feedbacks, and Carey Noll at CDDIS for keeping up with all the data and products used to generate these results. Final reprocessed due to come out soon. Best regards, Remi,