Abstract: A stray-wire sensor includes a vertical magnetic gradiometer (VMG) carried over the surface by ground vehicles or by low-flying aircraft. The VMG has a spot of sensitivity on the ground which stays nadir to the VMG itself. A Faraday shield surrounding the VMG screens out the near field electric dipole signals, and a ferrite rod core and winding inside act as an antenna sensitive to the near-field magnetic dipole signals which radiate from horizontal lying stray wires on the ground surface in the dirt of hidden by ground cover. The VMG depends on it being moved around over the ground so that magnetic signal gradients and reversals can be measured point-by-point. The nadir points which fall over a point along a long horizontal wire will express characteristic signatures in the signal gradients and phase reversals measureable in the antenna.