Magnetic anomaly detector

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A magnetic anomaly detector (MAD) is an instrument used to detect minute variations in the Earth's magnetic field. The term typically refers to magnetometers used by military forces to detect submarines (a mass of ferromagnetic material creates a detectable disturbance in the magnetic field). Military MAD equipment is a descendant of geomagnetic survey or aeromagnetic survey instruments used to search for minerals by detecting their disturbance of the normal earth-field.

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