[IGSMAIL-7921] Switch to IGb14 reference frame

Paul Rebischung Paul.Rebischung at ign.fr
Tue Apr 14 00:23:46 PDT 2020


Dear colleagues,

Since the end of the ITRF2014/IGS14 data input data (February 2015), a large number of IGS14 stations have been affected by position discontinuities and thus become unusable for operational reference frame alignments. Besides, the IGS14 coordinates of the remaining usable reference frame stations now need to be extrapolated by more than 5 years, which causes substantial errors.

For these reasons and in order to stabilize the reference frame alignment of the IGS products, the IGS is going to adopt an updated reference frame called IGb14, starting with products of GPS week 2106 (May 17, 2020).

IGb14.snx is available with some ancillary files at ftp://igs-rf.ign.fr/pub/IGb14:
* IGb14.snx      : IGb14 SINEX file
* IGb14.ssc      : IGb14 SINEX file without covariance matrix
* IGb14_core.txt : list of IGb14 core stations
* soln_IGb14.snx : discontinuity list to be used with IGb14.snx
* psd_IGb14.snx  : post-seismic deformation models to be used with IGb14.snx

IGb14 was obtained from a long-term stacking of daily IGS combined repro2/operational solutions of GPS weeks 730 to 2092 (see details in the comment section of the SINEX file). IGb14 is aligned in origin, scale and orientation to IGS14 via a subset of 233 selected stations. The switch from IGS14 to IGb14 should therefore not introduce discontinuities in the IGS operational product series.

Compared to IGS14, IGb14 benefits from 5 more years of input data, a revised discontinuity list and 9 additional stations. To illustrate the expected benefit of the switch from IGS14 to IGb14, the IGS combined SINEX solution of week 2093 was aligned to both reference frames. The number of RF stations used for both alignments and the RMS of the alignment residuals are given in the table below.

             |    RMS [mm]    |
 RF     #sta |   E    N    H  |
-------------|----------------| 
 IGS14   106 |  2.4  2.8  6.5 |
 IGb14   161 |  1.3  1.6  4.4 |
-------------|----------------|

Paul Rebischung, on behalf of the IGS Reference Frame Working Group


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