The quality analysis of the ITRF97 results is based more specifically on global residuals per solution (Table 2) as well as per site. All residuals on a site-by-site basis resulting from the combination are available in the file ITRF97.RESIDUALS. In this file, the following residuals are provided, per individual solution, for each station within each site, both for positions and velocities:

• (RX, RY, RZ) the 3 residual components in the geocentric frame;
• (RE, RN, RU) the 3 residual components in the local frame;
• (NE, NN, NU) the 3 normalized residual components in the local frame, such as,
  for example: , where is the uncertainty of the Easting component.

It should be noted that, since the individual solutions were mapped at their Epochs of Minimal Position Variance, this leads obviously to one epoch per station. Consequently, the post fit position residuals are naturally computed at the epoch of each station.

Table 2 : Global ITRF97 residuals per solution