Abstract: A system for detection of linear underground anomalies passing under surface roads comprises an electromagnetic (EM) gradiometer mounted on a vehicle trailer. A transmitter is mounted to the front bumper of a car or vehicle towing the trailer and provides carrier synchronization information to the EM-gradiometer. An opportunistic radio station can be used as an illuminator. The transmitter or ground wave from an opportunistic radio station directs radio waves down into the ground where objects like linear underground anomalies and their equipment will produce reflections and scattered waves. These reflections will have phase angles and magnitudes that can be interpreted for characterizing information about the linear underground anomalies. Each EM-gradiometer measurement is tagged with GPS location information and then stored in a database. Subsequent passes over the same roadways and tracks are compared (change detection) to the earlier stored data.

Abstract: An aerial electronic system for detection of surface and underground threats comprises an electromagnetic (EM) gradiometer flown aloft over the possible ground and underground threats to a convoy. The EM gradiometer is disposed in a Styrofoam torpedo shaped pod that is towed in flight behind an airplane. An illumination transmitter and loop antenna mounted to the airplane radiate a primary EM wave that travels down to the ground surface and penetrates beneath. Frequencies of 80 KHz to 1 MHz are selected according to whether the targets are laying on the surface or deeply buried. Detonation wire pairs, buried cables and pipes, and other conductors will re-radiate a secondary wave that can be sensed by the EM gradiometer. A reference sample of the transmitter signal is carried down a fiberoptic from the airplane to the towed pod. This signal is used in the synchronous detection to measure the secondary EM wave phase.

Abstract: An aerial electronic system for detection of surface and underground threats comprises an electromagnetic (EM) gradiometer flown aloft over the possible ground and underground threats to a convoy. The EM gradiometer is disposed in a Styrofoam torpedo shaped pod that is towed in flight behind an airplane. An illumination transmitter and loop antenna mounted to the airplane radiate a primary EM wave that travels down to the ground surface and penetrates beneath. Frequencies of 80 KHz to 1 MHz are selected according to whether the targets are laying on the surface or deeply buried. Detonation wire pairs, buried cables and pipes, and other conductors will re-radiate a secondary wave that can be sensed by the EM gradiometer. A reference sample of the transmitter signal is carried down a fiberoptic from the airplane to the towed pod. This signal is used in the synchronous detection to measure the secondary EM wave phase.