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Memoirs of the Kakioka Magnetic Observatory Vol.13 No.01 >Ready Reckoner for computing Geomagnetic Coordinates of Any Stations in Japan and its Vicinity

Ready Reckoner for computing Geomagnetic Coordinates of Any Stations in Japan and its Vicinity

Kuboki, T.

**Abstract**

Recently, many temporary stations for magnetic observations are set up to research the construction of upper mantle of the earth or special survey. It is frequent to calculate the geomagnetic coordinates of those stations. Formulas for it are simple as problem on mathematics, but the calculating work by means of those formulas is laborious. It takes one or two hours, and beside it is open to frequent errors.

The author devised a method using a set of reckoner in order to reduce the labour and errors. The calculating work by this method takes only several minutes. Its results are very exact so that errors are within the limit of ±0.’6．

This set of tables consist of 3 principal tables and 14 correcting tables. A principal table gives a principal value of geomagnetic longitude, latitude or angle for every 1°of are of geographical coordinate. Geomagnetic angle is the angle between geographic and geomagnetic meridian. Reference axis of the principal geomagnetic coordinate intersects with the earth surface at 291°E and 78.5°N in geographic coordinates.

Correcting tables give corrections for deviations of minute-order of arc in geographic coordinate and for change of geomagnetic reference axis and etc. This set of ready reckoner is usable only for stations in Japan and its vicinity.

Calculations of geomagnetic coordinates by the present method on some stations in Japan, whose geomagnetic coordinates have been reported already are shown, and some problems on them are discussed.

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