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Correcting compass declination


Compass declination is:


  Because the earth's magnetic field deviates from the geometrical north and south poles, a magnetic needle will indicate an azimuth that deviates from true north as shown in the picture.


 This deviation is called declination.

Declination varies depending on location.


 ・What is a magnetic field

 ・Geographic Survey Institute - Know Earth's Magnetic Field

 ・NGDC Geomagnetic Calculators


Method for correcting the electric compass's declination

 It is hard to correct a compass that uses a mechanical, magnetic needle.

 In the case of an electric compass, it is comparatively easy.  The steps to calibrate are shown below.


 (1)Create a table

  Create a table segmenting the mesh of declination angle data from the earth's surface.


Declination data (Make this into a table)



 (2)Correction calculation

  True north = magnetic north + declination data table value

A correction can be calculated using this method.