Figures and Statistics from the IGS Ultra-Rapid GPS Orbit Combination

Predicted orbit comparison figures

The plots below show the Weighted RMS (WRMS) and median differences (mm) of the individual AC and IGS combined orbit predictions with respect to the IGS RAPID products. The comparisons are performed on the first 6 hours (first 12 hours until week 1267) of the predictions (the second half of each IGU file), which are intended for real time (RT) applications. This gives a slightly optimistic assessment of the actual IGU RT accuracy since there is an 3-hour latency for each IGU update. For an idea of the rate at which the IGU accuracy degrades with prediction interval, please compare with the 24-hour prediction plots in the next subsection.

AC Ultra orbit RT prediction differences w.r.t. IGS Rapid

WRMS of AC Ultra-rapid orbits (raw) recent weeks GIF PS history GIF PS
WRMS of AC Ultra-rapid orbits (smoothed) recent weeks GIF PS history GIF PS
WRMS of IGU combined orbits compared to IGR recent weeks GIF PS history GIF PS
             
Median of AC Ultra-rapid orbits (raw) recent weeks GIF PS history GIF PS
Median of AC Ultra-rapid orbits (smoothed) recent weeks GIF PS history GIF PS
Median of IGU combined orbits compared to IGR recent weeks GIF PS history GIF PS
             
Orbit Prediction (Missing PRNs & Quality) recent weeks GIF PS

Orbit predictions compared to Rapid; Missing PRNs and Quality

GIF recent weeks cod emr esa gfz grg ngs sio usn whu
PS recent weeks cod emr esa gfz grg ngs sio usn whu


The plots below show the Weighted RMS and median differences (mm) of the IGS combined orbits with respect to the IGS RAPID products, but here the comparisons are performed over the full 24 hours of predictions. Only those values from the Ultra-rapid products issued for 00 UTC epochs are compared.

AC Ultra orbit 24h prediction differences w.r.t. IGS Rapid

WRMS of IGU combined orbits compared to IGR
(predictions over 24 h starting at 00 UT)		 recent weeks GIF PS history GIF PS
Median of IGU combined orbits compared to IGR
(predictions over 24 h starting at 00 UT)		 recent weeks GIF PS history GIF PS

Near RT observed orbit comparison figures

The plots below show the Weighted RMS and median differences (mm) of the IGS combined orbits with respect to the IGS RAPID products. These comparisons are performed over the full 24 hours of near real time observations (the first half of each IGU file). Only those values from the Ultra-rapid products issued for 00 UTC epochs are compared.

AC Ultra orbit near RT observed differences w.r.t. IGS Rapid

WRMS of IGU combined orbits compared to IGR
(observed over 24 h starting at 00 UT)		 recent weeks GIF PS history GIF PS
Median of IGU combined orbits compared to IGR
(observed over 24 h starting at 00 UT)		 recent weeks GIF PS history GIF PS

Orbit combination comparison figures

The plots below show the Weighted RMS differences (mm) of the individual AC orbits with respect to the IGS ULTRA-rapid products. The comparisons are performed over the entire 48 hours of the products.

AC Ultra orbit differences w.r.t. IGS Ultra-Rapid

WRMS of AC Ultra-rapid orbits (raw) recent weeks GIF PS history GIF PS
WRMS of AC Ultra-rapid orbits (smoothed) recent weeks GIF PS history GIF PS

Clock comparison figures

The plots below show the RMS differences (ns) between individual AC Ultra-rapid clock predictions and the IGS RAPID products. The comparisons are performed on the first 6 hours (first 12 hours until week 1267) of the predictions (the second half of each IGU file), which is intended for RT applications.

AC Ultra clock prediction differences w.r.t. IGS Rapid

RMS of AC Ultra-rapid clock predictions (raw) recent weeks GIF PS history GIF PS
RMS of AC Ultra-rapid clock predictions (smoothed) recent weeks GIF PS history GIF PS

The plots below show the Std Dev and RMS differences (ps) between the combined Ultra-rapid near real time clock observations and the IGS RAPID products. The Std Dev values are computed by removing a separate bias for each satellite clock, whereas this is not done for the RMS values. In the case where one uses these products with carrier phase data and estimates an ambiguity parameter for each station-satellite pair (such as for precise point positioning), the satellite clock biases will be absorbed by the ambiguity parameters, so the Std Dev statistics are appropriate. In other applications where no station-satellite bias parameter is estimated or where the underlying satellite time scale itself is of interest, then probably the RMS statistics are more suitable. These comparisons are performed over the full 24 hours of near RT observations (first half of each IGU file). Only those values from the Ultra-rapid products issued for 00 UTC epochs are compared.

AC Ultra near RT clock observed differences w.r.t. IGS Rapid

Std Dev of AC Ultra-rapid near RT clock observations recent weeks GIF PS history GIF PS
RMS of AC Ultra-rapid near RT clock observation recent weeks GIF PS history GIF PS

ERP comparison figures

The next plots show the difference between individual AC Ultra-rapid ERP solutions and the IGS Rapid product. The differences are shown for X-, and Y-pole, X-, and Y-pole rate, and LOD (length of day). The Ultra-rapid ERP values are taken from the observed half, not predictions, and only noon epoch values are shown to avoid interpolation. (Note that occasional spikes in the differences are caused when an AC misses a submission and their predicted ERP value was used rather than observed for that day.)

For the X-, and Y-pole figure the individual series are shifted by 1 mas for recent data and 2 mas for historic data.
For the X-, and Y-pole rate figure the individual series are shifted by 4 mas/day.
For the LOD figure the individual series are shifted by 0.2 ms/day for recent data and 0.4 ms/day for historic data.


AC Ultra ERP differences w.r.t. IGS Rapid

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 of the individual AC solutions with respect to the IGS ULTRA-rapid products.

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 weekly averages of translation, rotation, scale parameters of the individual AC solutions with respect to the IGS RAPID products.

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


Plots for the individual AC solutions with respect to the IGS ULTRA-rapid products.
The translations are shifted by 50 mm. The rotations are shifted by 2 mas.

Translations from:

GIF recent weeks cod emr esa gfz grg ngs sio usn whu history cod emr esa gfz gop grg ngs sio usn whu
PS recent weeks cod emr esa gfz grg ngs sio usn whu history cod emr esa gfz gop grg ngs sio usn whu


Rotations/Scale from:

GIF recent weeks cod emr esa gfz grg ngs sio usn whu history cod emr esa gfz gop grg ngs sio usn whu
PS recent weeks cod emr esa gfz grg ngs sio usn whu history cod emr esa gfz gop grg ngs sio usn whu


Figures for the individual AC solutions with respect to the IGS RAPID products.
The translations are shifted by 50 mm. The rotations are shifted by 2 mas.

Translations from:

GIF recent weeks cod emr esa gfz grg ngs sio usn whu igu history cod emr esa gfz gop grg ngs sio usn whu igu
PS recent weeks cod emr esa gfz grg ngs sio usn whu igu history cod emr esa gfz gop grg ngs sio usn whu igu


Rotations/Scale from:

GIF recent weeks cod emr esa gfz grg ngs sio usn whu igu history cod emr esa gfz gop grg ngs sio usn whu igu
PS recent weeks cod emr esa gfz grg ngs sio usn whu igu history cod emr esa gfz gop grg ngs sio usn whu igu


 

15 October 2024, originator IGS ACC