Frequecy-Domain ElectroMagnetic (FDEM)

FDEM surveying methods make use of the response of the ground to the propagation of EM fields, which are composed of an alternating electric intensity and magnetizing force. Primary EM fields are usually generated by passing alternating current through a small coil made up of many turns of wire (broadband sensors) or through a large loop of wire. The response of the ground is the generation of secondary EM fields and the resultant fields may be detected by the alternating currents that they induce to flow in a receiver coil by the process of EM induction.