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Application Note 2.
How Objects Appear to a Magnetometer
Iron objects tend to concentrate the magnetic field lines around
them distorting the Earth’s field. The magnetic field produced by
an iron object will tend to follow the same orientation as the
Earth’s field, and, if the object is moved, it will usually realign
with the new direction of the Earth’s field, because iron does not
form a strong permanent magnet.
If the iron object is flat in shape and horizontal (A), it will appear
to be rather like a horizontal bar magnet, and will form a North
Pole on its North side and a South Pole of similar strength
on the opposite side. However if the object has appreciable size
in a vertical direction (B), the bar-magnet will appear to be tilted
to match the earth’s field. In this case the North Pole will be
deeper than the South Pole and, at the ground’s surface it will
not be so strong. In this way we may find peaks of different
strength on either side of an iron object.
Figure 3 Diagram shows how the vertical thickness of a buried
object may cause an asymmetric response at the surface
in mid-latitude zones where the Earth's field has appreciable dip.
Summary of Contents for M-SCAN
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