On November 4, 2006, the IGS switched the reference frame from ITRF2000 to ITRF2005, and implemented new standards for GNSS data modelling that included a specific set of antenna phase centre variation (PCV) maps for all the GNSS satellite transmit antennas, and for most of the ground antennas (Byun and Bar-Sever, 2009). Before that date only the phase centre offsets of the satellite trans-mit antennas were standardized, and the ACs used a vari-ety of phase centre maps for the ground antennas modelling, including use of no phase maps at all.