Magnetic Variation or Declination.
Magnetic Variation or Declination is the horizontal angle formed between the geographic meridian and magnetic meridian.
It is caused by the terrestrial magnetism.
It is considered easterly or ( + ), when the magnetic north is eastward of geographic meridian.
And westerly or ( – ), when magnetic north is westward of geographic meridian.
It has different values on the Earth’s surface and for the same region varies over time.
This led to the printing on charts of the variation value for the measurement year and its annual fluctuation.
Based on these data we can determine the value of the magnetic variation for the current year.
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