ELECTRICAL RESISTIVITY SURVEY
DC resistivity techniques, sometimes referred to as Electrical Resistivity (ER), Electrical Resistivity Imaging (ERI) or Vertical Electric Sounding (VES), measure earth resistivity by driving a direct current (DC) signal into the ground and measuring the resulting potentials (voltages) created in the earth. From that data, electrical properties of the earth (the geo-electric section) can be derived and thereby the geologic properties inferred.
The technique consists of driving two electrodes into the earth to supply current to the ground. Two additional electrodes are used to measure the earth voltage (or electrical potential) generated by the current. Depth of investigation is a function of the electrode spacing. The depth of investigation is generally 20% to 40% of the outer electrode spacing, depending on the earth. The resistivity data is then used to create a hypothetical model of the earth and its resistivity structure (geo-electric sections). If borehole data or a conceptual geologic model is available, then a geologic identity can be assigned to the geo-electric units. A two-dimensional geo-electric section may be made up of a series of one-dimensional soundings joined together to form a two-dimensional section. The type of section produced depends on the acquisition parameters and the type of processing applied to the data.
Electrical Resistivity Tomography is carried out using multi-electrodes spaced at desired intervals along a linear profile.
The Company provides the following services using electrical resistivity imaging
- Estimating depth to bedrock, depth to water table, and depth to geo-electric boundaries
- Mapping and detecting geological features, such as, cavities and water channels
- Delineation of aggregate deposits for quarry operations
- Measuring earth resistance for electrical grounding circuits and cathodic protection
The Company follows ASTM International Standard Designation D6431-10 Guide in acquisition, processing and interpretation of Electrical Resistivity Survey data.