The systematic errors are within the aircraft receiver equipment being used to measure the radials from the stations and the aircraft's displacement from those radials.

The error will always be in the same direction, i.e. EITHER +5º OR -5º from each radial measured. NOTE: The number 5º in this case is a totally arbitrary number for illustration only.

If you look at the radials coming out of each of the VORs, only one position lies on the same side of each of the radials, that being position 1, which is +5º from each radial.

The other three positions 2, 3 and 4 lie on one or the other sides of each of the radials, e.g. Position 2 is +5º from the Northerly and Southerly VORs but -5º from the Easterly VOR.