GPS-only Analysis Products

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

Log of IGU changes

This log file lists events or other changes that might affect the IGU product quality or delivery schedule.

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 IGSRAPIDproducts. 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

 

The plots below show the Weighted RMS and median differences (mm) of the IGS combined orbits with respect to the IGS RAPIDproducts, 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

 

Jan Dousa at the Geodetic Observatory Pecnymaintains plotsof the recent radial, cross-, and along-track orbit differences of the real time portion of IGU products compared to the IGS Rapids, for each individual satellite.

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 RAPIDproducts. 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 IGSRAPIDproducts. 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

Orbit predictions compared to Rapid; Missing PRNs and Quality

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

 

The next plots show the weekly averages of the Helmert translation, rotation, and scale parameters of the individual AC solutions with respect to the IGSULTRA-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 RAPIDproducts.

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

 

Rotations/Scale from:

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

 

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

 

Translations from:

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

 

Rotations/Scale from:

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

Figures and Statistics from the IGS Rapid GPS Orbit Combination

Orbit and clock comparison figures

The WRMS plots below show the Weighted RMS (mm) of the individual AC orbit solutions with respect to the IGS Rapid (IGR) 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 Rapid products. The 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 (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. For display purposes, the daily clock Std Dev and RMS values from the Rapid combination summaries are weekly averaged.

On 11 April 2014, this webpage was updated to include following comparisons:

IGR and the observed part (IGA) of the 00h IGS Ultra-rapid product
IGR and the real-time part of the IGS Ultra-rapid product (denoted here as IGU**)
IGR and the IGS Real-time streams (denoted here as IGC**)

Note that IGC** are 24h SP3 files each containing four 6h segments (hours 4 thru 10) from each update interval of the IGS RT streams. The comparison with IGR is done daily over the full 24h of each IGC SP3. IGU** consists of 4 separate comparisons to IGR done each day over the first 6h of each IGS Ultra-rapid product.

The IGS Ultra-rapid orbit prediction errors grow with the sqrt(2). Each 6h segment within the 24h IGC file has a latency of 4 hours. The WRMS orbit differences between IGU** and IGC** for the first few weeks of this comparison are consistent with the errors for hours 4-10 of the IGS Ultra-rapid orbit predictions.

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

ERP comparison figures

The next plots show the difference between individual AC Rapid 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 figure the individual series are shifted by 1 mas.
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.

AC Rapid ERP differences w.r.t. 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
IGS Rapid ERP differences w.r.t. IGS Finals 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 solutions with respect to the IGS Rapid products.
“igu” is the 24 hours predicted orbit.

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 Rapid products.

The translations are shifted by 50 mm. The rotations are shifted by 1 mas.
“igu” is the 24 hours predicted orbit.

 

Scale/Translations from:

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

 

Rotations from:

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

Figures and Statistics from the IGS Final GPS Orbit Combination

Orbit and clock comparison figures

The WRMS plots below 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 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 (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. 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 jpl mit ngs sio igr | cod emr esa gfz grg jpl mit ngs sio igr
PS cod emr esa gfz grg jpl mit ngs sio igr | cod emr esa gfz grg jpl mit ngs sio igr

 

Rotations from:

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

Figures and Statistics for Broadcast Orbits wrt IGS Rapid Orbits

Orbit and clock comparison figures

The WRMS plots below show the Weighted RMS (m) of the Broadcast orbits (brd) with respect to the IGS Rapid product. The Clock Std Dev and Clock RMS plots show the standard deviations (ns) and RMS (ns) of the Broadcast clocks with respect to the IGS Rapid product. The Std Dev values are computed by removing a separate bias for each satellite clock, whereas this is not done for the clock RMS values. For Broadcast orbits and clocks, normally the RMS statistic is more suitable. Note that the intentional degradation of the GPS clock signals by Selective Availability (SA) was discontinued at midnight EDT on 01 May 2000, GPS Week 1060, Day 1 (or 04:00 UTC on 02 May). Since that change, civilian GPS users can obtain positioning and timing determinations that are more accurate than before by about a factor of up to ten. Clock statistics before Week 1060 are not shown here.

WRMS of Broadcast orbits recent weeks GIF PS history GIF PS
Std Dev of Broadcast clocks recent weeks GIF PS history GIF PS
RMS of Broadcast clocks recent weeks GIF PS history GIF PS

 

Orbit transformation results

The next plots show the weekly averages of the Helmert translation, rotation, and scale parameters of the Broadcast orbits 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

Figures and Statistics for Precise Point Positioning (PPP)

PPP Strategy:

A Precise Point Positioning (PPP) is performed using the ERPs, SP3 orbits, and satellite clocks from the IGS Final/Rapid combination as well as from the individual contributing Analysis Centers. Clocks and RINEX observations are decimated to 5-min intervals.

The PPP is done on a daily basis for each of the available stations defining the IGS Reference Frame (about 232 for IGS08/IGb08). For each set of AC orbits, ERPs, and satellite clocks, a PPP solution is done in three steps. Step 1 involves fitting the satellite positions from the SP3 orbit files to the extended CODE (6+9) orbit model using the associated ERPs in the ECF->Inertial transformation. Step 2 involves preprocessing of the clocks and RINEX observations to detect and eliminate clock jumps and cycle slips. Step 3 is the data reduction with iterative post-fit cleaning; outliers in the phase residuals are taken to be greater than 25 mm and outliers in the code residuals are taken to be greater than 2.5 m. A-priori modeling of the tropospheric delay is done using the Global Mapping Function (GMF) and Global Pressure and Temperature (GPT) model. Prior to 11 April 2013, The Niell Mapping Function (NMF) and standard meteorological data were used. The products from each AC are processed seperately; this way the cleaning for one AC has no effect on the results for the other ACs.

Helmert transformations are performed between the global network compiled from the PPP results and both the IGS Reference Frame and the IGS combined SINEX solution. The Helmert transformation parameters and station residual statistics are given over the past 7 days. North, east, up residuals (after the Helmert transformation) for each of the stations are presented including its mean and standard deviation over the past 7 days.

The PPP results give a measure of the internal consistency for each set of AC clocks, orbits, and ERPs. Over time, the PPP analysis also reveals information about the stability of station coordinates and the realization of a given reference frame.

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. Associated with this switch is a change to comparing with daily SINEX files, instead of a weekly one. The switch began impacting the Rapid PPP starting on 05-Sep-2012 (GPS Week 1704, day 3; mjd=56175).

Software:
Bernese GNSS Software v. 5.2, Developed by the Astronomical Institute of the University of Bern, Switzerland
(Bernese v. 5.0 was replaced on 11 April 2013)

PPP using Rapid Orbits and Clocks

PPP Rapid Transformations recent weeks GIF PS history GIF PS
PPP Rapid Rotations and Scales recent weeks GIF PS history GIF PS
PPP Rapid Station RMS
(IGS RF)
recent weeks GIF PS history GIF PS
PPP Rapid Station RMS (SINEX irf) recent weeks GIF PS history GIF PS

 

PPP using Final Orbits and Clocks

All AC and IGR/IGS results in one plot for each component.

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

 

PPP Final Station RMS (IGS RF) recent weeks GIF PS history GIF PS
PPP Final Station RMS (SINEX irf) recent weeks GIF PS history GIF PS

 

Figures for the individual ACs (and IGR/IGS).
Transformation parameters from the SINEX combinations are included for comparison.

Translations and Scale from:

GIF recent weeks cod emr esa gfz jpl mit igr igs history cod emr esa gfz jpl mit igr igs
PS recent weeks cod emr esa gfz jpl mit igr igs history cod emr esa gfz jpl mit igr igs

 

Rotations from:

GIF recent weeks cod emr esa gfz jpl mit igr igs history cod emr esa gfz jpl mit igr igs
PS recent weeks cod emr esa gfz jpl mit igr igs history cod emr esa gfz jpl mit igr igs

RAPID PPP

station repeatabilities referenced to

IGS frame IGR IGA COD EMR ESA GFZ JPL USN
SINEX combo IGR IGA COD EMR ESA GFZ JPL USN

FINAL PPP

station repeatabilities referenced to

IGS frame IGR IGA COD EMR ESA GFZ JPL USN
SINEX combo IGR IGA COD EMR ESA GFZ JPL USN