Earth Resistance

This technique is predominantly used to define the extent of sub-surface buildings and/or masonry although it can also identify soil-filled features. It uses electrical currents that are inserted into the ground with the resistance to this current measured. Earth Resistance Imaging (ERI) is commonly used to gather data from greater depths than is possible using magnetometry or earth resistance. Multiple electrodes are set-out along a profile line and, by taking readings with differing separations, it is possible to record variations in resistance with depth allowing the identification of geological boundaries, water table depth, buried alluvial channels, mass burials and large buried archaeological features