Magnetic declinationMagnetic declination
, also known as magnetic variation
, is the angle between magnetic North
, the direction of the magnetic North Pole
indicated by a magnetic compass
, and true North
, the direction of the North Pole
. Because the magnetic North Pole is not at the North Pole, it is necessary to compensate for the difference when using a compass for navigation
. Modern navigational compasses will usually include a declination adjustment that can be set to make the compass indicate true North instead of magnetic North.
Magnetic declination varies from place to place and over time. A prediction of the current magnetic declination for a given location can be obtained on-line from a web page  operated by the National Geophysical Data Center, a division of the National Oceanic and Atmospheric Administration of the United States.