- True north
"noted by the Chinese
polymath Shen Kuo in the11th century and possibly the egyptians over 6 millenia ago.True north: is if a line is drawn from the North Pole to the South pole it is 'TRUE NORTH'.True north is compared to magnetic north (the direction of the
magnetic north pole ) andgrid north (the direction northwards along the grid lines of amap projection ).The direction of true north is marked in the skies by the
north celestial pole . For most practical purposes, this is the position ofPolaris . However, due to theprecession 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. 5,000 years ago, the closest star to the celestial north pole wasThuban .On maps issued by the
United States Geological Survey , and theU.S. military , true north is marked with a line terminating in a five-pointed star. Maps issued by theOrdnance Survey contain a diagram showing the difference between true north, grid north and magnetic north at a point on the sheet.
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