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| Titel |
Estimation of GPS satellite antenna z-offsets from reprocessed SINEX files |
| VerfasserIn |
Ralf Schmid, Xavier Collilieux, Peter Steigenberger, Urs Hugentobler |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250040045
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| Zusammenfassung |
| Since November 2006 an absolute phase center correction model for GNSS satellite and
receiver antennas has been used within the International GNSS Service (IGS). This model,
called igs05.atx, comprises consistent phase center offset and variation values given in
ANTEX format. Generally, these correction values have not been changed in the meantime.
Solely values for new receiver antenna types or newly launched satellites have been
added.
With view to the upcoming transition to ITRF2008, a general update of the IGS
antenna phase center model is in progress that will be called igs08.atx. Therefore,
reprocessed weekly SINEX files of several IGS analysis centers (ACs) will be analyzed to
derive new GPS satellite antenna z-offsets. These values will be based on more data
(16 instead of 11 years) and more ACs than the values currently used, and they
will also cover the latest satellites launched in recent years. As selected station
coordinates will be fixed to ITRF2008 when back-solving the SINEX files, the
antenna model will be fully consistent with the corresponding terrestrial reference
frame.
For the z-offsets contained in igs05.atx this is not the case. At the time those
were estimated, the solutions could only be aligned to IGb00, an IGS realization of
ITRF2000, but not to ITRF2005. Whereas absolute receiver antenna corrections
were applied for these computations, the underlying reference frame was based on
relative corrections, and the effect of radomes could not be considered. Moreover,
an error in the mean vertical velocity of IGb00 caused a significant trend in the
z-offset time series of all satellites. Thus, they could only be given for a specific
epoch.
We will compare z-offset time series from the computations for igs05.atx and
igs08.atx to demonstrate the reduction of trends and the improvement of the overall
consistency. Resulting biases between individual ACs will highlight scale-related
discrepancies, and the general agreement between the two phase center models will be of
particular interest.
The transition to igs08.atx also provides the possibility to update the receiver antenna
calibrations, as discontinuities in the time series of station coordinates cannot be prevented
anyway. Thus, the percentage of IGS stations with state-of-the-art calibrations will
improve to about 70%. On the other hand, about 20% of the stations will still be
covered by uncalibrated radomes. We will analyze the distribution of stations with
inadequately calibrated antennas and show which local ties could be negatively affected. |
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