Electromagnetic (EM) research examines deposit conductivity induced by the electromagnetic field. The measurement system has two coils: transmitting and receiving. The transmitter produces a primary electromagnetic field, generating a secondary electromagnetic field in the deposit an the receiving coil records the secondary field size and the ratio between the primary and secondary fields. VLF (Very Low Frequency) method examines the secondary fields produced by the conducting deposits, found in soil, which are subjected to the original EM signal. This passive method uses radiation from strong military radio as the primary signal.
The EM-VLF method is one of many geophysical methods using the frequency parameter.
Electromagnetic (EM-VLF) surveys consist in measuring the conductivity of a medium by recording secondary fields generated by conductive bodies located in the substrate. This method allows measurements to be made without contact with the substrate.
In surveys conducted using the radio wave profiling technique, low-frequency radio wave signals [15-30 kHz] from strong military radio stations are used.