A range of methods by which magnetic or electrical fields generated in subsurface conductors by artificially induced eddy currents are measured. The term includes radar, electromagnetic ground conductivity, and VLF, but excludes those in which induction is insignificant, for example, resistivity and induced polarization, and those with insignificant depth penetration, for example, microwave sensing. The AFMAG method, which uses naturally generated electrical signals, is included, but magnetotelluric methods are not.