True North vs Magnetic North vs Geographical North

True north

True north (geodetic north) is the direction along the earth's surface towards the geographic North Pole.True geodetic north usually differs from(The direction a compass points toward the magnetic north pole), and from grid north (the direction northwards along the grid lines of a map projection). [1]Geodetic true north also differs very slightly from Astronomical true north (typically by a few arc seconds) because the local gravity may not point at the exact rotational axis of the earth.The direction of astronomical true north is marked in the skies by the north celestial pole. This is within about 1 degree of the position of Polaris, so that the star appears to trace a tiny circle in the sky each day. Due to the precession of the Earth's axis, true north rotates in an arc with respect to the stars that takes approximately 25,000 years to complete.

Magnetic North

The North Magnetic Pole is the point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downwards.

The North Magnetic Pole moves over time due to magnetic changes in the Earth's core.In 2001, it was determined by the Geological Survey of Canada to lie near Ellesmere Island in northern Canada at 81.3°N 110.8°W. It was situated at83.1°N 117.8°W in 2005.[2] In 2009, while still situated within the Canadian Arctic territorial claim at 84.9°N 131.0°W,it was moving toward Russia at between 34 and 37 miles (55 and 60 km) per year.As of 2012, the pole is projected to have moved beyond the Canadian Arctic territorial claim to 85.9°N 147.0°W.

Its southern hemisphere counterpart is the South Magnetic Pole. Since the Earth's magnetic field is not exactly symmetrical, the North and South Magnetic Poles are not antipodal: i.e., a line drawn from one to the other does not pass through the geometric centre of the Earth.

Geographical Pole

A geographical pole (also geographic pole) is either of the two points—the north pole and the south pole—on the surface of a rotating planet (or other rotating body) where theaxis of rotation (or simply "axis") meets the surface of the body. [3]The north geographic pole of a body lies 90 degrees north of the equator, while the south geographic pole lies 90 degrees south of the equator The Earth's actual physical North Pole and South Pole vary cyclically by a few meters over the span of each few years. This phenomenon is distinct from the precession of the equinoxes of the Earth, in which the angle of the planet (both axis and surface, moving together) varies slowly over tens of thousands of years.

Reference

1. ^ ^a b World Data Center for Geomagnetism, Kyoto. "Magnetic North, Geomagnetic and Magnetic Poles". Retrieved 2012-07-03.
2. ^ North Magnetic Pole Moving East Due to Core Flux, National Geographic, December 24, 2009
3. ^ "The Magnetic North Pole". Ocean bottom magnetology laboratory. Woods Hole Oceanographic Institution. Retrieved June 2012.