Yes, squaring will be needed. The two xy tables will be carrying a single bar of some sort for the hall probe along a Z axis.
Picture a 12 in DIA tube, 6 ft. long with an X-Y table at each end that will position a bar in the tube. A probe runs along the bar (Z axis)
to scan the inside of the tube, thus mapping the magnetic field. Positioning on X, Y, and Z.