Quest For The South Magnetic Pole
Fact Sheet #1: Why are there so many poles?
True Geographic Pole
Either of two points of intersection of the surface of the Earth with 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 AmundsenScott South Pole Station. Here there are many markers representing the
movement of the true geographic pole. 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
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 northwesterly direction.
The location of the south magnetic pole in 2007: 64.497° S and 137.684° E.
Geomagnetic Pole
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 south geomagnetic pole is at 78° 30' S and 111° E which is near Russia's
Vostok Station.
Pole of Inaccessibility
The furthest point from any Antarctic coasts. 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. They are protected as an historic site. When the site
was visited in January 2007, only the bust and plaque were visible.
Ceremonial Pole
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
placed on the Geographic Pole, but this pole moves 10m per year.
Directions
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.
Magnetic North
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.
Grid North
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.
Meridian
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.
Parallel
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.
Source: Ursula Ryan, AADC
For Australian Antarctic Division