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Magnetic Measurements >
Geomagnetic Surveys
Geomagnetic Surveys
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Direct measurements of the Earth magnetic elements
which serve for studying the spatial distribution of the Earth magnetic field (magnitude and direction of the
field in each point of the globe) are called magnetic surveys.
There are different ways of surveying: terrestrial, marine and aerial (aeromagnetic survey).
Results of magnetic surveys represent derived data obtained after processing raw data with certain algorithms and
applying required corrections (corrections for the ship speed, daily variation, topography etc).
Observation results (numeric values) of one or another element are put on the map for visual representation
of the distribution of the magnetic field on the Earth surface, equal values are connected with lines,
which in general are called isolines. Particularly lines of equal declination are called isogons, equal
inclination lines are called isoclinals and equal vertical or horizontal components lines are called isodynams.
A map with magnetic elements put on it is called magnetic map or a map with elements of the
field isolines.
Modern methods of map construction usually include such analytical procedures as mesh of nodes
regularization (alignment of the irregular mesh points, where measurements are taken, to regular grid
with its nodes that appear to be interpolated values of one of the field elements). Values of the regular grid
nodes interpolation may be solved with different methods depending on the chosen algorithm. This way such a map
is a graphical image of à certain analytical model.
It is a set of spherical harmonic analysis coefficients that is considered to be an analytical
representation of the global geomagnetic field, knowing which it’s possible to synthesize field value
at any point or set of points.
Global maps of the magnetic field elements are produced exactly this way and these data are also
sometimes represented as tables of synthesized values with certain pitch.
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