Magnetic declination

The magnetic declination (or magnetic variation) at any point on the earth is a property of the geomagnetic field defined as the angle that must be added or subtracted in converting between two kinds of directional information:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• the direction of the needle on a magnetic compass located there, and
• the direction of the earth's lines of longitude.

For points in the Northern Hemisphere, these are usually described as magnetic north and true north respectively. (In the Southern Hemisphere, visualizing the underlying physics and the practical calculations would be clearer with magnetic south and true south substituted.)

Related Topics:
Northern Hemisphere - Magnetic north - True north - Southern Hemisphere

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The agonic lines are the imaginary lines on the Earth surface along which the compass needle points to the geographic north and south, i.e. the magnetic declination is zero.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

 
Magnetic declination: "True" directions ►