Left: orientation of the X-to-K, X-to-Ka, and X-to-O vectors for the 194 sources used for the comparison before (thin line) and after (thick line) adjustment of large-scale systematic errors measured relative to the north, turning positive into the direction of right ascension. Right: uncertainty on the position angles versus the angular separation. The vertical (horizontal) lines represent the median values of the angular separations (position angle uncertainties) for each frequency.