It is a geophysical survey instrument used to measure electrical resistivity. and induction Electrical current to locate and determine the size of underground cavities, differences between different types of cavities, faults, fissures, depths between strata and rocks. as a survey tool That is popular because it is used in many types of surveys, whether it is geological or hydrogeological, exploration for mineral resources, find the direction of the flow of groundwater, find the direction of water seepage, monitor changes. Soil and rock conditions.