ERT electrical resistivity tomography is non-invasive surface method used to map subsurface resistivity and define geological features. ERT data are collected with automated multi-electrode resistivity meters. The chief advantage of ERT method is great accuracy of measurements as well as high immunity to electrical interferences. Depending on applied electrode array ERT survey allows to choose 1D, 2D or 3D imaging. Interpretation of ERT data provides information on the mineral deposit and its depth, presence of aquifers or on the source and extent of groundwater and soil pollution.