Electromagnetic induction (EM) uses the principle of induction to measure the electrical conductivity of the subsurface. A primary magnetic field is created in the space surrounding transmitting coil. A secondary current is generated from underground conductors, which results in an alternating secondary magnetic field that is detected by a receiving coil. The ratio of the magnitudes of the primary and secondary currents is proportional to the terrain conductivity.dsed
Unlike conventional resistivity techniques, no ground contact is required. This eliminates direct electrical coupling problems and allows much more rapid data acquisition.
Environmental Site Assessment
Site assessment surveys are performed as a part of Phase II surveys or as pre-drilling and pre-excavation surveys. Techniques used for characterization of a site include ground penetrating radar, terrain conductivity measurements and magnetics. The results define areas of debris, former excavation boundaries, void spaces, and foundations.
