Magnetic anomaly detector
A magnetic anomaly detector (MAD) is an instrument used to detect minute variations in the
by detecting their disturbance of the normal earth-field.History
Geoexploration by measuring and studying variations in the Earth's magnetic field has been conducted by scientists since 1843. The first uses of magnetometers were for the location of ore deposits. Thalen's "The Examination of Iron Ore Deposits by Magnetic Measurements", published in 1879, was the first scientific treatise describing this practical use.[2]
Magnetic anomaly detectors employed to detect submarines during
Satellite, near-surface and oceanic data from detectors was used to create the World Digital Magnetic Anomaly Map published by the Commission for the Geological Map of the World (CGMW) in July 2007.
Operation
The magnetic anomaly from a submarine is usually very small. One source estimates that it is only about 0.2 nT at a distance of 600 m.[5] Another source estimates that a 100 m long and 10 m wide submarine would produce a magnetic flux of 13.33 nT at 500 m, 1.65 nT at 1 km and 0.01 nT at 5 km.[6] To reduce interference from electrical equipment or metal in the fuselage of the aircraft, the MAD sensor is placed at the end of a boom or on a towed aerodynamic device.[7] Even so, the submarine must be very near the aircraft's position and close to the sea surface for detection of the anomaly, because magnetic fields decrease as the inverse cube of distance, one source gives a detection slant range of 500 m.[7] The size of the submarine, its hull composition and orientation, as well as the water depth and complexity of the natural magnetic field, determine the detection range. MAD devices are usually mounted on aircraft.[7] For example, one study showed that a horizontal detection range of 450–800 m, when aircraft was 200 m above a submarine, decreased to less than 150 m when the aircraft was 400 m above the submarine.[8]
If the sea floor has sunken ships, then submarines may operate near them to confuse magnetic anomaly detectors.[9]
MAD has certain advantages over other detection methods. It is a passive detection method. Unlike sonar it is not impacted by meteorological conditions; indeed above sea state 5, MAD may be the only reliable method for submarine detection.[8]
Other uses
For
See also
- Submarine detection system
- Autolycus, exhaust plume detector
References
- ISBN 9780850451634.
- ^ Note Outline: Geophysical Surveying Using Magnetics Methods, January 16, 2004, University of Calgary
- ISBN 978-0-7858-2226-4
- ^ "Victor Vacquier Sr., 1907–2009: Geophysicist was a master of magnetics", Los Angeles Times: B24, January 24, 2009.
- S2CID 204082945.
- ^ Yuqin Chen, Jiansheng Yuan. "Methods of Differential Submarine Detection Based on Magnetic Anomaly and Technology of Probes Arrangement": 446.
{{cite journal}}
: Cite journal requires|journal=
(help) - ^ a b c "Fundamentals of Naval Weapons Systems - Chapter 9 Underwater Detection and Tracking Systems".
- ^ S2CID 117237628.
- ^ Peter Howarth. China's Rising Sea Power. p. 93-94.