The International Terrestrial Reference Frame (ITRF97).

The ITRF97 (International Terrestrial Reference System) solution described in this Technical Note is a continuation of the new generation of realization of the International Terrestrial Reference System (ITRS), started with ITRF96. It is achieved by combining simultaneously station positions and velocities using full variance-covariance information provided, in SINEX format, by the IERS analysis centers. Moreover, a rigorous weighting scheme is used, based on the analysis and estimation of the variance components using the Helmert method. The reference frame definition (origin, scale, orientation and time evolution) is achieved in such a way that ITRF97 is in the same system as the ITRF96. In addition, station velocities are constrained to be the same for all points within one and the same site. The ITRF97 contains more than 550 stations located on 325 sites.