The data analysis was performed in three steps :

• Each individual solution was compared to the ITRF94 in order in one hand to estimate the transformation parameters of the system attached to the solution with respect to ITRF94 and, on the other hand, the level of agreement with the ITRF94 values.
• In order to assess the relative quality of the individual solutions, and their behaviour with respect to each other independently from the influence of local ties, a combination within each technique was also performed.
• A global combination was finally performed. Matrix Scaling Factors have been rigorously estimated during this combined adjustment which was iterated.

The ITRF96 global combination is achieved with the following properties :

• It includes the 17 selected space geodetic solutions provided by the IERS analysis centers and 70 constructed SINEX files containing positions and covariances, derived from local ties
• The reference frame definition (origin, scale, orientation and time evolution) of the combination is achieved in such a way that ITRF96 is in the same system as the ITRF94
• Velocities are constrained to be the same for all points within each site.