True geographic pole
The true geographic poles are the two points where the Earth's surface intersects the Earth’s axis of rotation. The location of this pole moves approximately 10m a year and is recalculated each year. The true south geographic pole is located near Amundsen-Scott South Pole Station. There are many markers at this site representing the movement of the true geographic pole over the years.
The distance between the south geographic pole and the south magnetic pole is approximately 2,858 kilometres. The geographic pole is also sometimes referred to as the geodetic pole.
South magnetic pole
The south magnetic pole is the point on the Earth’s surface where the direction of the Earth’s magnetic field is vertically upwards. The magnetic dip (the angle between the horizontal plane and the Earth’s magnetic field lines) is 90° at the magnetic poles. The south magnetic pole is not fixed and its position moves about 5 kilometres a year, presently in a north to north-westerly direction.
The location of the south magnetic pole in 2020 is 64.07°S, 135.88°E.
The Geomagnetic pole is either of two points of intersection of the surface of the Earth with the extended axis of a magnetic dipole which is assumed to be located at the centre of the Earth and approximates the source of the Earth’s magnetic field. It should not be confused with the magnetic pole which relates to the actual magnetic field of the Earth.
The location of the south geomagnetic pole in 2020 is 80.65°S, 107.32°E, which is near Russia’s Vostok Station.
Pole of inaccessibility
The furthest point from any Antarctic coasts is the pole of inaccessibility. It is located at approximately 83° S and 55° E, approximately 870 kilometres from the South Pole. The pole of inaccessibility was reached by a Soviet Antarctic Expedition for International Geophysical Year research work in 1958. Today a building, plaque and bust of Vladimir Lenin still remain, and are protected as an historic site. When the site was visited in January 2007, only the bust and plaque were visible.
Located near Amundsen-Scott South Pole Station. A red and white striped barber pole capped with a metallic chromium globe. Surrounding the barber pole are 12 flags representing the original Antarctic Treaty signatories. The barber pole was originally placed on the geographic pole, but this pole moves 10 metres per year.
Geographic or true directions
North-south is along any meridian and east-west is along any parallel, because of the way the graticule has been defined. These lines are perpendicular except at the poles. The direction determined by the orientation of the graticule is called geographic or true direction. True north is therefore the direction towards the north geographic pole.
The direction indicated by the north seeking pole of a magnetic needle influenced only by the Earth’s magnetic field. The direction of the magnetic pole is not usually parallel to the meridian. The difference between true north and magnetic north is called magnetic declination.
The northwards direction of a line of constant easting on a grid projection. When a rectangular grid is placed over the graticule of a map, the north direction of the grid will generally not coincide with true north. For example, when a UTM projection is used, grid north and true north only coincide at the central meridian. Away from the central meridian the difference between true north and grid north is known as the grid convergence.
A line approximating the surface of the Earth, from the north pole to the south pole and connecting points of equal longitude. The prime meridian, located at Greenwich, England, is the origin from which the numbering begins for identifying lines of longitude.
A circle approximating the surface of the Earth, parallel to the equator and connecting points of equal latitude.
Great circle distance
The shortest distance between two points on the surface of the Earth, assuming the Earth is spherical.