## ITRF94

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### Description

The ITRF94 solution is available on this server for wide distribution. The determination of this solution was a lenghty process for several reasons :

• The analysis strategy and the choice of the published results were redefined with regards to previous years. The new strategy was to perform a global combination of a selection of submitted solutions and then to compare the other solution to this combination. The basic criteria for this combination were :
• To obtain combined positions and velocities without use of a priori geophysical model (plate tectonic or postglacial rebound)
• To select the solutions (called class I) which provided full covariance matrices with adjusted velocities as well as good quality
• To select a datum without ERP constraints, with best orientation continuity with past BIH/IERS one, and with best estimate of origin and scale extracted from those solutions where this information was physically estimable (The selection was circulated in the IERS Working Group on ITRF Datum).
• The necessity to use a standard format (SINEX/ISEF1) to get individual solutions with full covariance matrix
• Various small misunderstandings between ACs and ITFS concerning exchanged data had to be clarified
• Delicate estimate of a scaling factor for each received covariance matrix in order to get a realistic combination
• Analysis of datum parameters and final selection

The computations were reiterated up to the point that we estimated that the solution fulfilled reasonably the previously described criteria. Finally a detailed analysis of results for each station has led to a classification of the ITRF94 coordinates for the points of the IERS Network.

### Files

The classification of coordinates includes four classes: A, B, C and Z. The meaning of these classes is described in the file ITRF94CLA.

A detailed description of the analysis can be found in ITRF94.REPORT.

The solution is presented through four tables giving coordinates, each table including a class of points and through two tables giving transformation parameters between ITRF94 and class I and class II submitted solutions. A third table is a compilation of transformations for various reference frames. For class A positions at 1993.0 and velocities are given. For the other classes, positions and for most of stations velocities also are given (we have removed velocities which were clearly unreliable).

The checks of consistency of EOP series with their corresponding terrestrial and celestial reference frames are described in file ITRF94.REPORT{.dlLink target=_blank}, which gives also the values to add to the IERS EOP series to make them consistent with the IERS reference frames. The individual comparisons are given in file ITRF94_EOP.CONSISTENCY.

In addition, a compressed SINEX file containing ITRF94 positions at 93.0 and velocities, is also provided : [ITRF94.SNX.gz](/ftp/pub/itrf/itrf94/ITRF94.SNX.gz){.dlLink target=_blank} available by FTP:

• host: itrf-ftp.ign.fr
• folder: pub/itrf/itrf94

All ITRF94 coordinate residuals on a site-by-site basis are available in file ITRF94.RESIDUALS.

### General information files available

• File iers.site{.dlLink target=_blank} contains the catalogue of the IERS sites containing those of the ITRF94. It gives the DOMES number, name, country, approximate longitude and latitude, plate (as indication for the application of the geophysical model NNR-NUVEL1A; this information has to be used carefully in some case : microplates, boundaries...).
• File iers_dir.sta{.dlLink target=_blank} contains the directory of the IERS stations ordered by their site DOMES numbers giving the site name, 4-char ID or/and CDP number and the description/inscription of each point.
• File iers_sta.occ{.dlLink target=_blank} contains a summary of the occupancies of the IERS stations by VLBI, LLR, GPS, SLR and DORIS instruments. The file is divided into the following data sets :
• Colocation : at least two techniques
• Multiple (simultaneous or successive for VLBI, GPS, SLR and DORIS)
• Single VLBI, GPS, SLR and DORIS
• File iers.ecc{.dlLink target=_blank} contains local eccentricities for IERS sites.