As decided at the EUREF TWG meeting of May 26, 2009 in Florence and announced on Oct. 2, 2009 by EUREF mail no 4647, the original EUREF densification of the ITRF2005 (released on Dec 12, 2008 by EUREF mail 4142) is now updated each 15 weeks taking the most recent EPN results into account. These regularly updated positions/velocities are the result of a multi-year adjustment of all the weekly combined EPN solutions in which outliers have been eliminated and station discontinuities were applied. Details are available through the Time Series Analysis web page at the EPN Central Bureau.
In order to provide the most reliable products, the EPN stations are categorized taking the station quality and the length of the available observation time span into account (Kenyeres, 2009):
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Only Class A stations are suitable as fiducial stations for the densification of the ETRS89. The associated files can be downloaded from the EPN Central Bureau; the most recent realization is available through the links:
In the ITRS:- EPN_A_ITRF2005.SSC, table with site positions (at epoch 2005.0) and velocities
- EPN_A_ITRF2005.SNX.Z, solution in SINEX format
- EPN_A_ETRF2000.SSC, table with site positions (at epoch 2005.0) and velocities
- EPN_A_ETRF2000.SNX.Z, solution in SINEX format
More details about the usage of the Class A stations for EUREF densifications are available from "Guidelines for EUREF Densifications" by Bruyninx et al.
For Class B stations, EUREF provides only position estimates at the epoch of minimal variance while the velocity estimates are not released because of their limited accuracy (caused by e.g. the short observation period of the station).
Used Reference Systems:
The International Terrestrial Reference System (ITRS), a global system with changing site coordinates due to the motion of the continental plates. The ITRS coordinates of EPN station change about 2,5 cm/y. The ITRS is mostly used for large scale scientific applications. It is also the system in which the precise IGS satellite orbits are given and it is the system from which other regional systems are derived.
The European Terrestrial Reference System (ETRS89), the regional European system derived from the ITRS (see "Guidelines for Reference Frame Fixing"). The ETRS89 is linked to the stable part of the Eurasian plate and site coordinates are almost constant. The ETRS89 is used as the standard precise GNSS coordinate system throughout Europe. Supported by EuroGeographics, this reference system forms the backbone for all geographic and geodynamic projects on the European territory both on a national as on an international level.
Transformation formula's between successive realizations of the ETRS89 and ITRS are available from the Memo by Boucher and Altamimi, 2008. Transformation parameters between ITRF solutions and ITRS and WGS84 parameters are available from the ITRF web site.
EPN Central Bureau - Royal Observatory of Belgium