RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 10, ES4003, doi:10.2205/2007ES000258, 2008

Geographical Map "Geomagnetic Field of the Earth''

2007ES000258-fig18
Figure 18
[35]  This map (Figure 18) was developed for the Defense Ministry of Russia and Rosgidromet. It has the following parameters: scale 1:25,000,000; isolines of the absolute value of horizontal component of the Earth's main magnetic field vector of strength ( |H| ). The values of isolines lie within the range from 500 to 40,000 nT with interval of 2000 nT, isolines of 500 and 1000 nT are added to ensure the better mapping of the horizontal component of the main geomagnetic field near magnetic poles, for which |H|=0; magnetic meridians of the Earth's main geomagnetic field, including the longitudes, where magnetic meridians intersect with the geographical equator and lie in the range from -160 to +180 with interval of 20o; magnetic equator with vertical component values Z=0 of the main geomagnetic field; for the periods of 1995-2005: the North magnetic pole has coordinates: 81oN and 110oW, and the South magnetic pole - coordinates 65oS, 138oE; availability of the geographical grid and geographical equator.

[36]  The map was developed using the data for the corresponding years for an altitude equal to 0, converting from a geocentric to geodetic system of coordinates. The calculations in reference points were carried out using the BGS program as described above. The special technology of data processing was developed for drawing isolines of horizontal component |H|, magnetic meridians and magnetic equator.

[37]  All data of the electronic map have geographic coordinates - a Greenwich longitude (in the range from -180o to +180o) and latitude (from -90o to +90o).

[38]  The data massifs of magnetic equator (the layer Magnetic equator) contain the curve of magnetic equator, the attributive database contains the value of vertical component Z of the main geomagnetic field ( Z=0 for magnetic equator). To the north of this curve Z is directed towards the Earth's interior, to the south - from the Earth's center.

[39]  The data massifs of the isolines of absolute value of horizontal component |H| of the main geomagnetic field (layer Isolines of IGRF horizontal component) contain the isolines of |H|, the attributive database for each isoline contains the corresponding value of |H|. These values range from 500 to 40,000 nT; isolines are provided for values of 2000, 40,000 nT with interval 2000 nT; isolines of 500 and 1000 nT are added for a better mapping of the main geomagnetic field near magnetic poles, corresponding to |H|=0.

[40]  The data massifs of the magnetic meridians of the main geomagnetic field (layer Magnetic meridians) comprise the curves of magnetic meridians, the attributive database for each curve comprises the longitude values, where a magnetic meridian intersects the geographic equator. These values range from -160o to +180o with interval 20o.

[41]  The data massifs of angle of declination D of the main geomagnetic field (layer Vectors of IGRF declination) contain 64,257 hatches of a transformed direction; a hatch is a vector with the length of ~0.5o. The initial points of hatches are located periodically in one degree of latitude and in one degree of longitude. The attributive database for each hatch contains the initial (non-transformed) numerical values of declination angle D expressed in degrees. An angle of declination is counted from the direction of a geographic meridian; for the eastern declination of vector of the horizontal component of the main geomagnetic field of the geographic meridian angle D is positive, for the western - negative.

[42]  The map was developed in a traditional paper variant, in digital variant and downloaded in a GIS at a scale of 1:25,000,000 in Mercator projection. The digital data contain the isolines of horizontal component |H| of the main geomagnetic field with recorded values of |H|, magnetic meridians with recorded values, at which magnetic meridians intersect with the geographic equator, transformed hatches of directions of declinations of the main field, magnetic equator, geographical objects (countries, oceans etc.), the legend.

[43]  The map's digital data are presented as the GIS database Geomagnetic field of the Earth, converted into compatible formats for the GIS ArcView and GIS "Neva'' [Zhalkovsky, 2001, 2002, 2004].


RJES

Citation: Zhalkovsky, Ye. A. (2008), Chart-making of the Earth's main magnetic field, Russ. J. Earth Sci., 10, ES4003, doi:10.2205/2007ES000258.

Copyright 2008 by the Russian Journal of Earth Sciences

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