Why does a compass needle point north?
As xprofessor said, the magnetised needle of the compass aligns itself with the earth’s magnetic field and the magnetic north pole is some distance from the true north pole. It is slightly west of true north. It also moves and on maps such as the UK’s Ordnance Survey maps and on sea charts you will see information about the position of magnetic north when the map or chart was printed and how to work out its current position – something like ‘Variation 7°55′ West (1999) decreasing about 5′ annually’. On ships and boats there is a further factor that has to be taken into consideration and that is the magnetic field created by ferrous metal and electrical equipment on the vessel – this is called Magnetic Deviation and has to be calculated so that it can be added to or subtracted from Magnetic Variation – the result of that calculation is the Magnetic Declination for that particular vessel. If you don’t do these calculations you could end up hundreds of miles from where you wanted to be on
