Unexploded Ordnance

Highly sensitive magnetometers play a key role in the search for unexploded ordnance (UXO) as many of the UXO contain a considerable amount of ferrous material. By scanning the magnetic field of the area under investigation, anomaly maps can be generated that show positions of ferrous objects as deviations in the average magnetic field. More advanced interpretation of the magnetic data allows deriving information on the UXO size, depth, and subsurface orientation. In UXO applications, typically the vertical component of the magnetic field is used. Basic setups use a mobile magnetic recording station and a fixed base station to measure the natural field variations. Almost all modern UXO detection setups use arrays of magnetometers to derive spatial derivatives of the magnetic field. Arrays are moved over the area of interest by vehicles, helicopters, or by foot. All gathered data is geo-referenced typically by utilizing differential GPS systems.

Magnetometers used in UXO applications need to be very sensitive as the deviations caused by the UXO may be quite small compared to the earth’s magnetic field. In addition, a large dynamic range is needed for the same reasons. The towing speed and sampling frequency of the magnetometer define the data density of the acquisition. Typical sampling frequencies are in the 1 Hz (foot) to 200 Hz (Helicopter) range. To ensure correct derivation of spatial derivatives the sensors of an array need to be synchronized in time. Modern fluxgate sensors are ideal for UXO applications. They combine the necessary sensitivity and dynamic range with high sampling frequencies and cost effectiveness. LEMI provides a wide range of analog and digital fluxgate sensors with or without total field compensation. See our fluxgate magnetometer product page or contact us at info@lemisensors.com for further information.