Positional differences in α and δ between Gaia-CRF3 and ICRF3 S/X for the 3142 common sources. The 259 defining sources in ICRF3 are shown as filled red circles, other sources as black crosses. Top: differences in mas. Errors bars representing the quadratically combined uncertainties in the two catalogues are shown only for the defining sources. Bottom: same differences divided by the quadratically combined uncertainties in the two catalogues. No error bars are shown in this plot, as they would all be ±1 unit.