IGS

International GNSS Service

Data Reprocessing Campaign

a first full reanalysis of all IGS GPS data collected since 1994

IGS
OBJECTIVE
The Analysis Centers (ACs) of the International GNSS Service are in the process of reanalyzing the full history of GPS data collected by the IGS global network since 1994 in a fully consistent way using the latest models and methodology. This is the first such full reprocessing by the IGS, but it is expected to be repeated in the future as further analysis changes are made.
SUMMARY
OF
PRODUCTS
The expected Analysis Center and combined IGS products include:
    daily GPS orbits & satellite clocks
    • 15-minute intervals (SP3c format)
    • satellite clocks in IGS timescale (loosely aligned to GPS time)
    daily satellite & tracking station clocks
    • 5-minute intervals (clock RINEX format)
    • in IGS timescale (loosely aligned to GPS time)
    daily Earth rotation parameters (ERPs)
    • from SINEX & classic orbit combinations (IGS erp format)
    • x & y coordinates of pole
    • rate-of-change of x & y pole coordinates
    • excess length-of-day (LOD)
    weekly terrestrial coordinate frames with ERPs
    • with full variance-covariance matrix (SINEX format)
    possible other products ?
    • ionosphere maps, tropospheric zenith path delays, etc
    • not part of this first campaign
ANALYSIS
CENTERS
The participating Analysis Centers contributing complete solutions to this effort are:
    CODE — Center for Orbit Determination in Europe, Switzerland
    EMR — Natural Resources Canada, Canada
    ESA — European Space Operations Centre (ESOC), ESA, Germany
    GFZ — GeoForschungsZentrum/Potsdam, Germany
    JPL — Jet Propulsion Laboratory, USA
    MIT — Massachusetts Institute of Technology, USA
    NGS — National Geodetic Survey, NOAA, USA
    PDR — GeoForschungsZentrum/Potsdam & Technical University of Dresden, Germany
    SIO — Scripps Institution of Oceanography, USA

In addition, some centers provide weekly SINEX solutions to help densify the terrestrial reference frame, particularly for GPS stations located near tide gauges (associated with the TIGA Pilot Project); work is underway to perhaps include associated satellite orbits and clocks:

    GTZ — GFZ TIGA, Germany
    ULR — University of La Rochelle, France

Summaries of the analysis strategies and procedures for each AC are posted at the IGS Central Bureau. Submitted AC solution files are posted at this GFZ site.

The product combination centers are:

    NRCan — Natural Resources Canada, Canada
    • SINEX combination — as of mid-Feb. 2009, results posted for years 2000-2008 (see below)
    NCL — University of Newcastle-upon-Tyne, UK
    • SINEX combinations
    GFZ — GeoForschungsZentrum/Potsdam, Germany
    NRL — Naval Research Laborartory, USA
    • clock & timescale combination results not yet available
FEATURES
OF DATA
ANALYSES
Essential elements of the analysis procedures used by all participating centers include:
TEST
RESULTS
To evaluate analysis and combination procedures, the ACs have provided test solutions for the first quarter of year 2000. Results from those tests are posted here.
ISSUES
TO BE
RESOLVED
There are several remaining issues to be addressed:
    all ACs need to maintain updated analysis summaries, including operational & reprocessing ACs
    • SIO last updated 31 Oct. 2005

    verify that all necessary IGS metadata files are current & complete
    • all historic & discontinued stations in the IGS master SINEX template file igs_with_former.snx
FILENAMING
AND
ARCHIVING
The following filenaming and archiving conventions have been adopted for this first and future reprocessing campaigns:
    IGS reprocessing campaign numbering
    • Since over the coming years we expect that there will be successive reprocessings, we will declare that each has a 1-character number to designate it. The present campaign will be "1". It will run from now till at least the end of 2009, probably.
    • Do we really need to think about more than 9 reprocessings now? That will be for a period of probably about 20 years. Many other things will likely change over that time.

    AC & combination file deposits
    • ACs should deposit standard Finals-like reprocessed solution files to the CDDIS Global Data Center (only) in their normal file delivery areas but under new subdirectories .../repro.
    • The AC and combination filenames must indicate the reprocessing campaign sequence number by using names of the type:
          CC#WWWWD.typ.Z
      where the standard center code "CCC" is changed to "CC#" and "#" is the particular reprocessing sequence number.
    • Those AC files are automatically moved to the standard public product archive directories but in new subdirectories
          /gps/products/WWWW/repro#
      where # is the particular reprocessing sequence number. During the reprocessing, the combination products will also be put in these subdirectories.
    • As with standard operational files, if an AC or combination center resubmits a newer version of any reprocessed solution file it will overwrite any older version.

    move to operational status
    • When the current 1st reprocessing campaign reaches its conclusion and the results are certified to be of a quality at least as good as the original operational solutions, then the present operational files will be moved downward to
          /gps/products/WWWW/orig
      subdirectories for permanent archiving.
    • At the same time, the 1st reprocessed files will be symbolically linked from
          /gps/products/WWWW/repro1/CC1WWWWD.typ.Z
      back up to the standard product directories to become the new operational products using the current standard IGS product names, from the earliest reprocessed week through 1459:
          /gps/products/WWWW/repro1/CC1WWWWD.typ.Z
          -> /gps/products/WWWW/CCCWWWWD.typ.Z
    • The present operational product files for weeks 1460 onward will remain in place and should be consistent with the 1st reprocessing products for weeks 1459 and earlier. (In fact, the original operational AC solutions during 2008 -- weeks 1460 through 1512 -- will also be recombined at the SINEX level to ensure stricter consistency in the handling of time series discontinuities and some other details. These recombinations are posted in repro1 subdirectories too, and will be moved to the operational directories at the end of the campaign. However, there will be no other recombined products nor new AC solutions.)
    • In this way, users should always be able to access the latest, most consistent set of IGS products by always downloading files from the standard product directories using the standard names.
    • On the other hand, users must take care to check for processing consistency when mixing recently downloaded files with older files. README and other advisory information will be posted and distributed to caution users on this point.

    future reprocessings
    • The same approach will be used with any future reprocessing campaigns, by creating sequentially new
          /gps/products/WWWW/repro#
      product directories, etc.
SCHEDULE
 The following schedule is suggested:
    Feb. 2008 — begin full reprocessing phase
    • start with data for week 1459 (23-29 Dec 2007)
    • then work backwards in time, hopefully back to 1994.0
    • the operational Final products from week 1460 forward should be consistent with the reprocessing so that the continuous span from 1994 onward will eventually become the official IGS product set

    02-06 June 2008 — IGS workshop
    • evaluate progress for initial phase of reprocessing

    January 2009 — prepare IGS submission for ITRF2008
    • all available solutions (with sufficient AC redundancy) submitted on a sliding schedule up January 2009 will be used to form a preliminary time series of weekly repro1 SINEX combinations:
      • earlier — years 2007-2005 to be submitted to CDDIS
      • 14 Nov. 2008 — year 2004 to be submitted to CDDIS
      • 28 Nov. 2008 — year 2003 to be submitted to CDDIS
      • 12 Dec. 2008 — year 2002 to be submitted to CDDIS
      • 26 Dec. 2008 — year 2001 to be submitted to CDDIS
      • 09 Jan. 2009 — year 2000 to be submitted to CDDIS
    • the preliminary repro1 time series will then be submitted to the IERS ITRF Product Center to be included in the ITRF2008 multi-technique combination
    • it was originally expected that the IGS time series would cover at least the period 2000 - 2008 (inclusive)
    • this period was extended in May (see below) to cover the additional years 1997 - 1999 (inclusive), which were submitted by late July

    10 February 2009 — submission deadline for ITRF2008 input solutions
    • all technique combined solutions due to ITRF Product Center of the IERS
    • first preliminary ITRF2008 results & discussions at EGU General Assembly, 19-24 April 2009 in Vienna
    • final ITRF2008 solution to be released 15 July 2009

    May - July 2009 — extend IGS submission for ITRF2008

    IGS solution for ITRF2008 — some assessment results are given below

    later 2009 — finish repro1 products
    • form full set of repro1 orbit & SINEX combination products using all available AC solutions during period 1994 - 2007
    • repro1 products will be merged with standard operational IGS Final products for period since week 1460 (since 30 December 2007) for complete coverage from 1994 to present
    • schedule for completion of repro1 reanalysis work by ACs (as of 22 Jul 2009):
      • 14 Aug 2009 — year 2007 to be submitted to CDDIS
      • 21 Aug 2009 — year 2006 to be submitted to CDDIS
      • 28 Aug 2009 — year 2005 to be submitted to CDDIS
      • 04 Sep 2009 — year 2004 to be submitted to CDDIS
      • 11 Sep 2009 — year 2003 to be submitted to CDDIS
      • 18 Sep 2009 — year 2002 to be submitted to CDDIS
      • 25 Sep 2009 — year 2001 to be submitted to CDDIS
      • 02 Oct 2009 — year 2000 to be submitted to CDDIS
      • 09 Oct 2009 — year 1999 to be submitted to CDDIS
      • 16 Oct 2009 — year 1998 to be submitted to CDDIS
      • 23 Oct 2009 — year 1997 to be submitted to CDDIS
      • 30 Oct 2009 — year 1996 to be submitted to CDDIS
      • 06 Nov 2009 — year 1995 to be submitted to CDDIS
      • 13 Nov 2009 — year 1994 to be submitted to CDDIS
    • final cutoff dates for any replacement AC solutions (updated 12 November 2009):

      • 16 Nov 2009 — last submissions for years 2001-2007 at CDDIS
      • 23 Nov 2009 — last submissions for years 1997-1999 at CDDIS
      • 30 Nov 2009 — last submissions for years 1994-1996 at CDDIS

      • it remains to be seen if enough usable solutions will be available for 1994
      • final weekly SINEX combinations are expected by the end of Dec 2009
ITRF2008
SUBMISSION
IGS solution for ITRF2008 — combined solution files submitted to IERS ITRF Product Center
Consistency of the IGS contribution to ITRF2008 (2009)
  • presentation by Rémi Ferland at the European Geosciences Union 2009 General Assembly
Reprocessed polar motion results from the ITRF2008 combination
  • analysis of IGS GPS-only polar motion results submitted for ITRF2008, illustrating the time evolution of the quality of the IGS polar motion time series over the 12.5 year period from 1997.0 through 2009.5
Quality assessment of the ITRF2008 (2009)
  • presentation by Z. Altamimi, X. Collilieux, and L. Métivier at the Fall 2009 American Geophysical Union Meeting
ITRF2008 station position residual time series
  • station position residuals from long-term linear stackings of solutions from each contributing technique, including IGS
  • note: the adjustment of weekly Helmert alignment parameters to form the long-term frames has probably absorbed some portion of the non-linear variations of individual stations (e.g., due to time-varying surface loading), especially from the vertical component
CURRENT
PROCESSING
STATUS

year 2000 test period

The status of test reprocessing, effective 06 May 2008:

File type codes:
  x - snx sinex
  e - erp earth rotation parameters
  o - sp3 orbits (eph)
  c - clk clocks
  s - sum summary

---------------------------------------------------------
WEEK yyyy ddd   es1    gf1    mi1    ng1    pd1    si1
               xeocs  xeocs  xeocs  xeocs  xeocs  xeocs
---------------------------------------------------------
1042 1999-360  1177_  _____  11771  117_1  117__  117_1
1043 2000-002  1177_  _1771  11771  117_1  117__  117_1
1044 2000-009  1177_  _____  11771  117_1  117__  117_1
1045 2000-016  1177_  _____  11771  117_1  117__  117_1
1046 2000-023  1177_  _____  11771  117_1  117__  117_1
1047 2000-030  1177_  _____  11771  117_1  117__  117_1
1048 2000-037  1177_  _____  11771  117_1  117__  117_1
1049 2000-044  1177_  _____  11771  117_1  117__  117_1
1050 2000-051  1177_  _____  11771  117_1  117__  117_1
1051 2000-058  1177_  _____  11771  117_1  117__  117_1
1052 2000-065  1177_  _____  11771  117_1  117__  117_1
1053 2000-072  1177_  _____  11771  117_1  117__  117_1
1054 2000-079  1177_  _____  11771  117_1  117__  117_1
1055 2000-086  1177_  _____  11771  117_1  117__  117_1
1056 2000-093  _____  _____  11771  117_1  117__  117_1
1057 2000-100  _____  _____  11771  117_1  117__  117_1
1058 2000-107  _____  _____  11771  117_1  117__  117_1
1059 2000-114  _____  _____  11771  117_1  117__  117_1
1060 2000-121  _____  _____  11771  117_1  117__  117_1
1061 2000-128  _____  _____  11771  _____  _____  _____
---------------------------------------------------------

Test campaign status summary (year 2000; weeks 1042 to 1060):
  es1 : 2007-11-07  (no files at CDDIS; posted directly to GFZ)
  mi1 : 2008-05-01
  ng1 : 2008-01-02  (no files at CDDIS; posted directly to GFZ)
  pd1 : 2007-07-16  (no files at CDDIS; posted directly to GFZ)
  si1 : 2007-06-23  (no files at CDDIS; posted directly to GFZ)

status for operational years 2007 and earlier

The status of repro1 reprocessing, effective 03 December 2009:

-------------------------------------------------------------------------
AC  2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994
-------------------------------------------------------------------------
AC submissions:
CO1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE
EM1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ---- 
ES1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ----
GF1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE
GT1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ---- ---- ---- ----
JP1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ---- ----
MI1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ---- ---- ---- ----
NG1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ----
PD1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE
SI1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE
UL1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE ---- ----

SINEX combinations:
IG1 DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE DONE
-------------------------------------------------------------------------
Plots of the statistical results from those weeks that have been reprocessed so far can be found at this website maintained at NRCanada by Rémi Ferland.
RESULTS
AND
ASSESSMENTS
Repro1 preliminary product combinations for evaluation:

SINEX TRF & ERP preliminary combination results ftp directories for preliminary weekly orbit combination summary reports
  • provided by GeoForschungsZentrum/Potsdam (GFZ), Germany
Repro1 final product combinations:

SINEX TRF & ERP final combination results Availability of reprocessed products ITRF2008 station position residual time series
  • station position residuals from long-term linear stackings of solutions from each contributing technique, including IGS
  • note: the adjustment of weekly Helmert alignment parameters to form the long-term frames has probably absorbed some portion of the non-linear variations of individual stations (e.g., due to time-varying surface loading), especially from the vertical component
Assessments & use of repro1 products:

Quality assessment of the ITRF2008 (2009)
  • presentation by Z. Altamimi, X. Collilieux, and L. Métivier at the Fall 2009 American Geophysical Union Meeting
Quality assessment of GPS reprocessed terrestrial reference frame (2009)
  • presentation by X. Collilieux, Z. Altamimi, L. Métivier, and T. van Dam at the Fall 2009 American Geophysical Union Meeting (ppt)
Reprocessed polar motion results from the ITRF2008 combination
  • analysis of IGS GPS-only polar motion results submitted for ITRF2008, illustrating the time evolution of the quality of the IGS polar motion time series over the 12.5 year period from 1997.0 through 2009.5
Reprocessed polar motion assessments — for period 2005 - 2007
  • results shown are for the latest AC solutions, which may not be the same as some earlier solutions used for the ITRF2008 submission; also not all ACs had solutions available at the time of ITRF2008 submission; all AC solutions will be used in the final repro1 combination
Validating Earth orientation series with models of atmospheric & oceanic angular momenta (2009)
  • presentation by R. Gross at the Fall 2009 American Geophysical Union Meeting
ITRF2008 ERP comparisons with IGS repro1 (25 March 2010)
  • comparison by Z. Altamimi of preliminary ITRF2008 combinations by IGN & DGFI with IGS repro1 (IG1) series
ITRF2008 & IGS repro1 polar motion comparisons with AAM+OAM (28 March 2010)
  • comparison by J. Kouba of preliminary ITRF2008 combination results for polar motion by IGN & DGFI as well as by IGS repro1 (IG1) with AAM+OAM excitation
Preliminary reprocessed orbit assessments — for period 2005 - 2007
  • results shown are for preliminary AC solutions, which may not be the same as some earlier solutions used for the ITRF2008 submission or final solutions submitted later; also not all ACs had solutions available at the time of ITRF2008 submission; all AC solutions will be used in the final repro1 combination
Reprocessed orbit assessments — for 3 equal periods from Aug. 1999 - Dec. 2007
  • results shown are for the latest AC solutions, which may not be the same as some earlier solutions, and the final IG1 combination; the analysis of day-boundary discontinuities considers conventional XYZ 1D magnitudes, as well as along, cross, and radial components
Preliminary analysis of IGS reprocessed orbit and polar motion estimates (2009)
  • presentation by J. Ray and J. Griffiths at the European Geosciences Union 2009 General Assembly
Assessment of the orbits from the 1st IGS reprocessing campaign (2009)
  • presentation by J. Griffiths, G. Gendt, Th. Nischan, and J. Ray at the Fall 2009 American Geophysical Union Meeting
Multi-technique reprocessing and combination using "space-ties" (2009)
  • presentation by T. Springer, F. Dilssner, D. Escobar, M.Otten, I. Romero, and J. Dow at the Fall 2009 American Geophysical Union Meeting
Quality of GRACE orbits using the reprocessed IGS products (2009)
  • presentation by Z. Kang, B. Tapley, S. Bettadpur, and H. Save at the Fall 2009 American Geophysical Union Meeting
Assessment of 3D hydrologic deformation using GRACE and GPS (2009)
  • presentation by C. Watson, P. Tregoning, K. Fleming, R. Burgette, W. Featherstone, J. Awange, M. Kuhn, and G. Ramillien at the Fall 2009 American Geophysical Union Meeting (ppt)
Results from the new IGS time scale algorithm (2009)
  • poster presentation by K. Senior and J. Ray at the Fall 2009 American Geophysical Union Meeting (ppt)
Results from the new IGS time scale algorithm (2010)
  • poster presentation by K. Senior and J. Ray IGS 2010 Workshop, Newcastle upon Tyne, UK, 28 June 2010 (ppt)
External comparison of EOP results (2010)
  • presentation by R.S. Gross at IGS 2010 Workshop, Newcastle upon Tyne, UK, 30 June 2010
IGS reprocessing -- Summary of orbit/clock combination and first quality assessment (2010)
  • presentation by G. Gendt, J. Griffiths, Th. Nischan, and J. Ray at IGS 2010 Workshop, Newcastle upon Tyne, UK, 30 June 2010
ITRF2008 and the IGS contribution (2010)
  • presentation by Z. Altamimi at IGS 2010 Workshop, Newcastle upon Tyne, UK, 28 June 2010
Status of IGS core products (2010)
  • presentation by J. Ray and J. Griffiths at IGS 2010 Workshop, Newcastle upon Tyne, UK, 28 June 2010
FUTURE
PLANS
Interactions of the IGS reprocessing and the IGS antenna phase center model (2009)
  • presentation by R. Schmid, P. Steigenberger, U. Hugentobler, R. Dach, M. Schmitz, and Florian Dilssner at the Fall 2009 American Geophysical Union Meeting
Preparations for the 2nd IGS Reprocessing Campaign (2009)
  • poster presentation by J. Ray at the Fall 2009 American Geophysical Union Meeting

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