Capacitive-resistive imaging system

A capacitive-resistive imaging system for imaging an environment e.g. subterranean geological formation comprises a plurality of conductive electrodes 111-114 supported on a substrate 118, and have a side directed away from the substrate. The electrodes are galvanically isolated from the environment to be imaged, and capacitively couple thereto, and have a dielectric coating 120 on at least the side directed away from the substrate. The dielectric constant of the dielectric coating is higher than 6, advantageously much greater than 6. This encourages an electric field induced into the environment from the electrodes to penetrate further into the environment, and reduces coupling to the substrate. The coating may be neoprene, tantalum pentoxide, strontium titanate, barium titanate or calcium copper titanate. The system has application in down-hole imaging, monitoring of constructions, foundations, and elsewhere.