Electrical Resistivity Tomography (ERT) is a non-destructive geophysical tool, an advanced technique of Electrical Resistivity Imaging (ERI).

It measures spatial variations in potential differences in response to induced current. The potential differences then are recalculated to the resistivity of the subsurface. A 2-D or 3-D geologic model, based on these mapped variations in subsurface resistivity and external constraints, is generated.

Resistivity (ρ), like density, is an intrinsic property of a material. Resistivity is mostly a function of lithology, porosity, clay content, permeability, fluid saturation and fluid salinity.