OFTEN USED: In open-field metal surveys such as UXO surveys, USTs, well heads, etc.
Electromagnetic Induction (EMI): EMI instruments contain two sets of coils located on opposite ends of the tool. One set of coils is used to transmit a primary magnetic field, which generates an electrical current into the ground. The induced current then generates a secondary magnetic field, which is sensed by the coils in the receiver end of the instrument. The EMI is moved over the surface without contacting it, so it is not affected by the terrain. EMI results are affected, however, by surface features such as vehicles, reinforced concrete, and buildings. They will not be used near above-ground obstructions.
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Data collected by the EMI unit indicates the conductivity of the soil or objects buried underneath it. This data is post-processed and displayed in a color-coded contour map which shows relative changes in conductivity. This contour map will be provided by GPRS for interpretation by the client.
