Frequency Domain Electro Magnetic (FDEM) induction involves generating electromagnetic fields which induce currents in the earth which in turn cause the subsurface to create secondary magnetic fields. By measuring the magnetic fields, subsurface properties and features can be deduced. This method measures the magnitude and the phase of the induced currents, which are related to the subsurface electrical conductivity. Electrical conductivity is a function of the soil and rock matrix, percentage of saturation, and the conductivity of the pore fluids. FDEM instruments provide two measurements simultaneously; the electrical conductivity data and the in-phase component, which responds to magnetic susceptibility and metal.
In certain cases, depths of up to 50 meters can be mapped.
IES uses Iris Instruments PROMIS 10. The PROMIC 10 instrument is a multi-frequency, multi-spacing 3 component slingram type EM System for sounding and profiling.
FDEM Software and Data Processing:
IES uses a combination of proprietary software and Iris Instruments Emsys software to process FDEM data.
FDEM survey in the Western Sahara using Iris Instruments PROMIS system.