To investigate the interoperability of the various GNSS constellations
we compute epochwise the positions of European
permanent GNSS receivers by analyzing data simultaneously from different GNSS
constellations.
Use RINEX 3.02 data freely available within the MGEX data base. Process pseudoranges in ionofree
combination, and broadcast ephemeris. Use as apriori
coordinates official ITRF2008/IGb08 values.
Solve for 3 coordinates, 1 clock offset for each GNSS constellation, 1
Tropospheric Zenith Delay (ZTD) at each computation epoch.
The computation is made daily for a sample of European GNSS sites, and
different receiver types. This Web site is updated on a weekly basis, beginning
Jan.1, 2014.
Our goal is to provide data, in tabular and plot format (see Keyword File Type), enabling
one to assess (see Keyword Parameter):
Parameter = Position: epochwise departures in
North East Up from a priori position
Parameter = Post fit residuals : differences between measured ionofree pseudorange and computed
pseudoranges, using estimated coordinates, clock
offsets and TZD
Parameter = Time Offset: Offset of the GNSS time scale relative to the
GPS time scale
Parameter = TZD: estimate of the TZD from the combined multiGNSS solution
In
addition we provide in Daily estimates of clock
offsets and drift relative to GPS daily values obtained, for each day, by Matlab’s “robust linear regression” of the epochwise values of the parameter Time Offset.

The Position data enable to assess the accuracy of the multiGNSS point positioning relative to exact coordinate
values, and the stability in time;

The Post fit residuals tell us about the goodness of the fit, and the
removal of GNSS dependent biases, particularly time biases.

The Time Offset data tell us about the amount of misalignment of the
time scales kept by the various GNSS relative to a reference time scale, which
we assume to be GPS

The TZD data tell us about the epoch by epoch Tropospheric Zenith Delay.

The Time Offsets of the same receivers are very close, for a given GNSS.
However Time Offsets measured with different receivers for the same GNSS may
vary. This leads to a quantitative estimate of
receiver dependent biases.
An analysis of intersystem biases for
multiGNSS positioning
Andrea
Dalla Torre • Alessandro Caporali
GPS Solutions (2014) DOI
10.1007/s1029101403882