Definition of Magnetic Declination,Inclination

[Manish Bhat]

I wish to know what exactly magnetic declination and inclination means. I used to feel that angle of declination was constant throughout the Earth equalling≈11.3°.But, it apparently isn't.
Then, why is so much significance attached to 11.3° if it is not universally constant?

 

[CWatters]

The magnetic north pole is offset from true north by about 11 degrees. eg draw two lines from the center of the Earth to magnetic and true north. The angle at the center is about 11 degrees.

However the error you see on a compas depends on where you are at the time. If you are standing in the right place on Earth the difference could be be zero. That's the Magnetic declination.

http://en.wikipedia.org/wiki/Magnetic_declination

http://en.wikipedia.org/wiki/Earth's_magnetic_field