Electromagnetic (TEM)

Electromagnetic (TEM) surveying methods make us of the response of the ground to the propagation of electromagnetic field. This response vary according to the conductivity of the ground (in S/m). Primary TEM fields are generated using a alternating current in a loop wire (coil) or a natural TEM source. 

(a) In-Loop TEM, (b) Moving-Loop TEM, (c) Fixed-Loop TEM

The reponse of the ground is the generation of a secondary TEM field.  The resultant field is detected by the alternating currents that thery induce in a receiver coil.