Figures and Statistics from the IGS Final GPS Orbit Combination

Orbit and clock comparison figures

The WRMS plots below (the first two rows) show the Weighted RMS (mm) of the individual AC orbit solutions with respect to the IGS Final products. The Clock Std Dev and Clock RMS plots show the standard deviations (ps) and RMS (ps) of the individual AC clock solutions with respect to the IGS Final products. The solid lines show weighted ACs and the dashed lines show unweighted solutions as of today.

The clock Std Dev values are computed by removing a separate bias for each satellite/station clock, whereas this is not done for the clock RMS values. In the case where one uses these products with carrier phase data and estimates an ambiguity parameter for each station-satellite pair (i.e. most positioning applications), the satellite clock biases will be absorbed by the ambiguity parameters, so the Std Dev statistics are appropriate measures to assess the consistency of the solutions.

In other applications where no station-satellite bias parameter is estimated or where the underlying satellite time scale itself is of interest, the RMS statistics may be useful. The larger RMS differences between the AC clocks stem from a few different factors. For satellite clocks, these differences mainly come from differences in how the ACs treat differential code biases (DCBs); most of the ACs use similar differential code biases (e.g. those provided by COD); however, when an AC uses a different set of DCBs it can show larger satellite clock RMSs. For the station clock RMS's, differences in the number of stations and the satellites processed can result in differences in the station clock RMS statistics.

Because of the relative nature of clocks, and since the AC clocks are re-aligned before combination, the main statistic to control the quality of the AC clocks is the clock Std Dev (and not the clock RMS).

The clock figures currently show combined satellite and station clock statistics. We are working on displaying separate satellite and station clock statistics for better visual comparisons. These separate statistics are available in the clock summary files (*.CLS.SUM) files. For display purposes, the daily clock Std Dev and RMS values from the Final combination summaries are weekly averaged. For display purposes, the daily clock Std Dev and RMS values from the Final combination summaries are weekly averaged.

Starting on 19-Aug-2012 (GPS Week 1702; mjd=56158), the IGS Finals products switched from being based on weekly SINEX integrations to being based on daily ones.

WRMS of IGS Final orbits (raw) recent weeks GIF PS history GIF PS
WRMS of IGS Final orbits (smoothed) recent weeks GIF PS history GIF PS
Std Dev of IGS Final clocks recent weeks GIF PS history GIF PS
RMS of IGS Final clocks recent weeks GIF PS history GIF PS

ERP comparison figures

The next plots show the difference between individual AC Final ERP solutions and the IGS Final product. The differences are shown for X-, and Y-pole, X-, and Y-pole rate, and LOD (length of day).

For the X-, and Y-pole plots the individual series are shifted by 0.5 mas for recent data and 1 mas for historic data.
For the X-, and Y-pole rate plots the individual series are shifted by 2 mas/day for recent data and 4 mas/day for historic data.
For the LOD plots the individual series are shifted by 0.2 ms/day.

AC Final ERP differences with IGS Finals

X-Pole recent weeks GIF PS history GIF PS
Y-Pole recent weeks GIF PS history GIF PS
X-Pole Rate recent weeks GIF PS history GIF PS
Y-Pole Rate recent weeks GIF PS history GIF PS
LOD recent weeks GIF PS history GIF PS


Orbit transformation results per AC

The next plots show the weekly averages of the Helmert translation, rotation, and scale parameters for the individual AC orbit solutions, with respect to the IGS Final products, compared to each other.

Trans. Rot. Trans. Rot.
GIF recent weeks Scale X Y Z X Y Z history Scale X Y Z X Y Z
PS recent weeks Scale X Y Z X Y Z history Scale X Y Z X Y Z


The next plots show the daily Helmert scale, translation, and rotation parameters for the individual AC orbit solutions separately, with respect to the IGS Final products. The orbit rotation plots also show associated polar motion (PM) offsets to check for rotational consistency (-dPMy with RX; -dPMx with RY). Recall that small AC SINEX rotational offsets were applied in the orbit combination process to all the AC orbit and PM values in order to align them consistently to the current IGS reference frame.

The translations are shifted by 50 mm. The rotations are shifted by 1 mas.


Scale/Translations from:

    recent weeks      history
GIF cod emr esa gfz grg jgx jpl mit ngs sio igr | cod emr esa gfz grg jgx jpl mit ngs sio igr
PS cod emr esa gfz grg jgx jpl mit ngs sio igr | cod emr esa gfz grg jgx jpl mit ngs sio igr

Rotations from:

    recent weeks      history
GIF cod emr esa gfz grg jgx jpl mit ngs sio igr | cod emr esa gfz grg jgx jpl mit ngs sio igr
PS cod emr esa gfz grg jgx jpl mit ngs sio igr | cod emr esa gfz grg jgx jpl mit ngs sio igr


 

24 September 2025, originator IGS ACC