Precise Transfer Measurement of the Magnetic Axis to Outside Monuments

The paper describes a new, precise method for the transfer of the magnetic quadrupole axis to the outside survey monuments. The magnetic axis is determined by the rotating coil method. The transversal coil position is shifted until the measured dipole component is at a minimum. Two optical targets are placed directly onto the coil ends. While the coil rotates slowly these targets perform a circular motion. The centers of these circles define the rotating axis of the coil in a very precise way. This axis is then transferred to several outside monuments using two laser trackers.