Which way is North?
Like many simple sounding questions there should be a simple answer. But in this case it depends on which way you consider North to be as there are three different directions to travel North.
So here is a quick rundown on what the heck is going on.
First of all there is TRUE NORTH.
As you know the Earth spins around an axis (like an apple with a pencil through it) and the ends of this axis are called the North Pole and the South Pole. So, in this North’s case, True North is a line pointing from where you are to the North Pole.
Next there is GRID NORTH.
This is quite easy to see, if you have a UK ordinance survey map, as it has straight lines (Northings) going vertically up the map. These lines are all meant to also point to True North: well that’s what you get taught on most map reading courses. Is this true? No.
Only one of the lines on the UK ordinance survey maps actually points directly at True North / The North Pole. This particular line is known as The Central Meridian: it stretches from just to the left of the Isle of Wight near Bournemouth, up to Birmingham and Bradford then towards Berwick on Tweed and just off the coast near Aberdeen. After this it just keeps on going all the way to the North Pole. All other vertical lines on your map are out by a few meters and the further away from our Bournemouth to Aberdeen line, the further away from True North they are. So folk in Wales, Cornwall, Norfolk, etc. need to take care when navigating with a map if you going a long way. Does this deviation really mater when map reading? Not if you’re just walking around the hills, but if you’re laying a long gas pipe or building a motorway, then yes, it really does.
Lastly there is MAGNETIC NORTH.
As you know the Earth has a magnetic field and the ends of magnetic fields are called poles. Your compass has a metal pointer in the dial and this also has a magnetic field. Opposite poles attract so your compass pointer will point at the end of the Earth’s magnetic field which is known as the Magnetic North Pole. As this magnetic field is created in the molten sections of the Earth it (being fluid) moves around. As few years ago it was under Canada, now it’s moving towards Russia.
So your compass needle is following local magnetic flux lines which are generally pointing at the Magnetic North: a location which is continually moving.