Remanent ground response is induced by rapid high current in a transmit coil. The transmit coil remains at zero current for a sufficient time for the remanent ground response to be sensed in a receive coil. A rapid high voltage and a sustained low voltage establish and maintain a stable current in the transmit coil followed by a zero current period. The sequence is repeated with a stable negative and followed by positive currents and a zero current. The receive coil is repeatedly interrogated at zero current between switch closings connecting in the transmit coil. Combined ground remanence and target eddy current signals are received during the constant current periods, and the ground remanence signals sensed during zero transmit coil current are subtracted from the combined signals.