 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "True north" – news ·newspapers ·books ·scholar ·JSTOR(May 2012) (Learn how and when to remove this message) |
True north is the direction alongEarth's surface towards the place where the imaginary rotational axis of the Earth intersects the surface of the Earth on itsnorthern half, the TrueNorth Pole.True south is the direction opposite to the true north.
It is important to make the distinction frommagnetic north, which points towardsan ever changing location close to the True North Pole determined byEarth's magnetic field. Due to fundamental limitations inmap projection, true north also differs from thegrid north which is marked by the direction of the grid lines on a typical printed map. However, thelongitude lines on aglobe lead to the true poles, because the three-dimensional representation avoids those limitations.
Thecelestial pole is the location on the imaginarycelestial sphere where an imaginary extension of the rotational axis of the Earth intersects the celestial sphere. Within a margin of error of 1°, the true north direction can be approximated by the position of thepole starPolaris which would currently appear to be very close to the intersection,tracing a tiny circle in the sky eachsidereal day. Due to theaxial precession of Earth, true north rotates in an arc with respect tothe stars that takes approximately 25,000 years to complete. Around 2101–2103, Polaris will make its closest approach to the celestial north pole (extrapolated from recent Earthprecession).[1][2][3] The visible star nearest the north celestial pole 5,000 years ago wasThuban.[4]
On maps published by theUnited States Geological Survey (USGS) and theUnited States Armed Forces, true north is marked with a line terminating in a five-pointed star.[5] The east and west edges of the USGS topographic quadrangle maps of the United States aremeridians oflongitude, thus indicating true north (so they are not exactly parallel). Maps issued by theUnited KingdomOrdnance Survey contain a diagram showing the difference between true north, grid north, and magnetic north at a point on the sheet; the edges of the map are likely to follow grid directions rather than true, and the map will thus be truly rectangular/square.[citation needed]
 | This article aboutgeography terminology is astub. You can help Wikipedia byadding missing information. |