Electrical Resistivity Tomography

We offer a non-destructive and cost-effective solution for surface imaging

Electrical Resistivity Tomography

Electrical resistivity tomography (ERT) is a non-destructive geophysical subsurface-imaging technique and is widely used in mineral prospecting, hydrological exploration, environmental investigation and civil engineering, as well as archaeological mapping. RAY SPEED ​​collects ERT data rapidly with an automatic 120 multi-electrode resistivity meter. It is a very useful method characterising the sub-surface materials in terms of their electrical properties. Variations in electrical resistivity (or conductivity) typically correlate with variations in lithology, water saturation, fluid conductivity, porosity and permeability, which may be used to map stratigraphic units, geological structure, sinkholes, fractures and groundwater. The survey data is processed to produce graphic depth sections of the thickness and resistivity of subsurface electrical layers. The resistivity sections are correlated with ground interfaces such as soil and fill layers, aquifers or soil-bedrock, interfaces, to provide detailed information on subsurface natural resources and geological conditions. ERT is extremely useful for understanding the sub-surface formations and for depth estimations of natural resources. 2D and 3D subsurface imaging is possible only with multi electrodes.

Data Acquisition

The acquisition of resistivity data involves the injection of current into the ground via a pair of electrodes and then the resulting potential field is measured by a corresponding pair of potential electrodes. The field set-up requires the deployment of an array of regularly spaced electrodes, which are connected to a central control unit via multi-core cables. Resistivity data are then recorded via complex combinations of current and potential electrode pairs to build up a pseudo cross-section of apparent resistivity beneath the survey line. The depth of investigation depends on the electrode separation and geometry, with greater electrode separations yielding bulk resistivity measurements from greater depths.

ERT Applications