Description

Electro-magnetic (EM) methods can be used to measure subsurface ground conductivities and hence resistivity information.

EM instruments work by creating a current that is induced into the ground from a transmitter coil. A magnetic field produced by the transmitter generates an electric current in the ground, which in turn generates a magnetic field, which can be detected by the receiver.).

Ground conductivity will increase with the presence of metals, ions or clay material in the strata.

The main advantage of EM methods is the fact that no probes need to be placed into the ground, resulting in a rapid and cost effective method of surveying large areas prior to undertaking more detailed survey.

EM systems can be used to map geological variations, groundwater The contaminants or any subsurface feature associated with changes in the ground under most geological conditions including those of high surface resistivity such as sand, gravel and asphalt.

Very cost-effective way of determining conductivity changes; however, can be seriously affected by metallic debris, metal pies and electrical cables, particularly High voltage lines.