Figures and Statistics from the IGS experimental Multi-GNSS Orbit Combination
Experimental Multi-GNSS Combination
In line with the IGS Multi-GNSS Experiment (MGEX) and with the increasing
trend in the availability of Multi-GNSS products through different analysis
centres, the IGS Analysis Centre Coordinator (IGS ACC) is trialling an
experimental MGEX orbit combination by adapting the existing combination
software. The intention is to compare how the next version of the combination
software will perform against the existing software; therefore, the MGEX orbit
combinations are not considered to be the final products at the moment. These
combinations also aim at comparing how different analysis centres perform
considering the MGEX products. They also encourage more contribution from
the analysis centres to the MGEX products.
The experimental MGEX products are made available on a weekly basis, with a
delay up to 13 to 20 days, similar to the final combination. Since the purpose
of the experimental phase is to include as many MGEX submissions as possible,
the combination includes rapid MGEX submissions as well as final submissions
combined together. As the eventual aim is to inlude as many submissions as
possible in the combination, the current GPS-only (and GLONASS-only)
submissions are also included as long as there is a maximum of one submission
from each AC for each constellation. In case of the ACs having both GPS-only
(or GLONASS-only) and MGEX submissions, only the MGEX submission is used and
the GPS-only or GLONASS-only solution is only used for comparison.
The AC SINEX transformations with respect to the current IGS reference frame
are not applied in the current Multi-GNSS orbit combinations. The orbit combination
is performed separately for each constellation, using the same weighted average
approach used in the current software for GPS orbit combination. The results
from different constellations are then compiled into one summary file and one
sp3 file available
Currently, only orbit combinations are available for the Multi-GNSS products.
The plots below showing the Weighted RMS (WRMS) of the the individual AC orbit
solutions (including MGEX solutions) with respect to the combined orbits, as
well as those showing the estimated transformation parameters between
individual ACs and the IGS combined orbits, are useful for assessing the
repeatabilities of the MGEX products by different analysis centres.
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 combined products, compared to each other.