How GEM’s Sensors Help Detect Underwater Bombs

GEM Systems produces magnetometers for a variety of applications – even for scouring out still-dangerous bombs hidden underwater.

Our technology has been strapped to a rig dangled some 30 metres underneath a helicopter as it is sent flying out over the water. The lowest part of the rig, which contains GEM’s sensitive magnetometer equipment, flies just two metres above the surface of the water. This tight span is carefully measured by a downward-pointing laser positioned towards the back of the rig. The distance does not leave much in the way of wiggle room, making for a very narrow margin of error for the helicopter pilot, as if the rig strikes the surface it could result in a disaster and the destruction of the rig or even the helicopter itself. The air-suspended rig – which looks a bit like a crop duster, with a horizontal bar holding five sensor extensions (ten in total) – contains potassium sensors that only GEM manufactures.



Image: history.ca

Flying low over the water within what amounts to a hair’s breadth of the water, the rig picks up on the magnetic field of any unexploded ordnance below. Old-fashioned analog detection techniques to find buried or hidden bombs involved an operator waving his or her detecting instrument over the target (or survey) area, and listening closely to their headphones for audio feedback indicating the presence of ordnance.

But now, the job is done digitally. The sensors on the rig soaring just above the water surface look for anomalies in Earth’s magnet field below. Bombs (such as World War II-era ordnance) and other items containing iron create small-scale distortions of the magnetic field. The rig then sends this raw data to a connected computer system for analysis, where a specialist will look for tell-tale spikes in a chart or graphic display of the magnetic field indicating that a bomb may be sitting in wait below.