The comparison of the phase lag of different oriented or dislocated antennas permits the determination
of direction of the wave. This is realized by various methods of antenna arrays, e.g. crossed loop
antennas in magnetic direction finders. Dipole arrays are used in interferometric antennas.
For 2D location only 2 receiving stations are necessary, for 3D location at least one antenna must
determine the elevation angle. The uncertainty in location determination depends on the angular
difference φi − φj and is largest for differences close to 0
◦
or 180
◦
. Operational networks consist
therefore of at least 3 stations