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Concerning the direct reading magnetic compass:
  • A
    acceleration errors are due to the compass deviation.
  • B
    errors of parallax are due to the oscillation of the compass rose.
  • C
    turning error is due to the vertical component of the earth`s magnetic field.
  • D
    reading error.

The pendulous magnet inside the direct reading magnetic compass will align itself with the magnetic flux lines of the Earth’s magnetic field. But these magnetic lines are not straight lines spread equally around the Earth. They’re straight and horizontal close to the Equator, but the higher the latitude, the more these lines tend to converge towards the Earth’s poles. Therefore, they will become more and more inclined until being fully vertical at the pole. As a consequence, the pendulous magnet will also increasingly tilt towards its vertical, as the compass approaches the pole.

The turning errors are directly related to the vertical component of the magnetic field of the Earth. The higher the dip angle induced by the vertical component, the larger the turning errors.

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