Multi-electrode resistivity surveys allow for the collection of depth and volume information of subsurface structures through electrical measurements at the surface. This represents a versatile non-invasive method to accurately assess a wide variety of subsurface features. Electrodes are arranged in various arrays at the surface, and current is passed through the source-detector system; it is the variations in this transmitted current that is recorded. By varying the electrode separation and location we can obtain information on subsurface changes in soil resistivity and map these variations with position and depth.
Applications of ERI include mineral prospecting, monitoring of ground water flow and archaeology to name a few. It has been employed to determine the extent of saline intrusion at coastal sites, and in void assessment, especially in clay-rich conductive areas where GPR is ineffective.
Using modern equipment and good survey design this method can be rapidly applied over a large area investigating both shallow and deep soil conditions.