Resistivity tomography utilizes borehole cables which can be combined with surface electrodes to provide a high-resolution resistivity image of the subsurface. The advance of utilizing boreholes is the fact that one can obtain higher resolution at depths where normal surface resistivity will have much lower resolution. Another useful application is areas where the target of interest is located beneath a structure such as a building which will prevent the use of conventional surface resistivity.
Data is efficiently acquired with a multi-electrode system such as the AGI Supersting R8 system which allows for data collection using the bipole-bipole and/or dipole-dipole command files. An example of data is shown here where the objective of the investigation was the mapping of the thickness and extent of soil-crete columns for foundation purposes. The tomography technique was capable of accurately mapping the thickness of the soil-crete, and identify zones of poor soil-crete formation due to the presence of gravel layers in this particular case.