Abstract: A pair of magnetometer units symmetrically displaced from a reference measuring point along one axis and at least one magnetometer unit displaced from the reference point along a second axis perpendicular to the first axis respectively sense three and two directional field components of a magnetic source along two axes at each of the unit locations parallel to the first and second axes and a third axis perpendicular thereto at each of said pair of units. Total field strength and field gradients of the magnetic source are calculated from measurement sensor signals supplied by the magnetometer units to determine the position of the magnetic source relative to the reference point and its magnetic moments.