True north is a
navigational term referring to the direction of the
North Pole relative to the navigator's position. Its concept was first discovered and noted by the Chinese
polymath Shen Kuo in the
11th century.True north is compared to
magnetic north (the direction of the
Magnetic North Pole) and
grid north (the direction northwards along the grid lines of a
map projection).The direction of true north is marked in the skies by the celestial north pole. For most practical purposes, this is the position of
Polaris. However, due to the
precession of the Earth's
axis, true north rotates in an arc that takes approximately 25,000 years to complete. In 2002, Polaris was at its closest approach to the celestial north pole. 2,000 years ago, the closest star to the celestial north pole was
Thuban.
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The direction from an observer's position to the geographic North Pole. The north direction of any geographic meridian. 1/4/71
Direction joignant la position d'un observateur au pôle nord géographique. Direction d'un méridien géographique quelconque. 1/4/71
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