In geophysics, electrical measurement techniques to estimate near-surface impedances were initially developed in the context of mineral prospecting by Conrad Schlumberger in 1911 [ 39 , 941 ] and have been widely used in subsurface investigations ever since. Geoelectric imaging is used world-wide in industry, consultancy and academia, and is the subject of considerable ongoing research and development. Terminology in geophysics has evolved and what was initially referred to as “vertical electrical sounding” (a one-dimensional layered Earth problem) has been refined to Electrical Resistivity Tomography (ERT). Electrical Resistivity Imaging (ERI) is also used in some literature as an alternative to the use of ERT. Resistivity (units: Ωm), the reciprocal of conductivity (units: S/m), is generally the preferred unit when discussing geological phenomena.