soon to be G2238. On the other hand GLONASS is using PZ-90.11, which is close to ITRF2008 at epoch 2011.0 and is using 2010.0 epoch (that means when you use reference transformation to PZ-90.11 you will get January 2010 date). See also Earth-centered, Earth-fixed coordinate system Earth orientation parameters Geodetic datum International Celestial Reference System and its realizations Terrestrial reference frame World Geodetic System References External links Forward and backward transformations using 14 parameters Helmert Convertor between ITRF realisations with changing the epoch and tectonics, tectonics for it What is ITRF? Terrestrial reference systems and frames (PDF; chapter 4 of IERS Conventions 2010) Geodetic datums