EM Conductivity (Frequency-Domain EM)
Definition
A non-contact method using a transmitter coil to induce eddy currents in the ground and a receiver coil to measure the secondary magnetic field, yielding apparent conductivity. Instruments like the Geonics EM31 and EM38 cover ground rapidly for reconnaissance surveys.
- Method
- Frequency-domain electromagnetic induction
- Measures
- Apparent ground conductivity
- Example instruments
- Geonics EM31, EM38
- Contact
- Non-contact, rapid coverage
Common questions
How does EM conductivity differ from ground-penetrating radar?+
It measures the bulk electrical conductivity of soil and buried material through induced currents, rather than reflecting a radar pulse off subsurface interfaces, so it responds differently to metal, moisture, and disturbed ground.
What forensic target does it detect well?+
Disturbed soil and buried metal, since grave fill and other disturbed ground typically differ in conductivity from the undisturbed soil around it, producing a detectable anomaly during reconnaissance.
Related terms
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- Magnetic Susceptibility
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- Thermoremanent Magnetisation (TRM)
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- Wenner Array
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