Finding North - Adjusting for Magnetic North

Did you know that there are three different variations of North?

So, let's look at finding "North".

When taking a compass bearing on the map you will have aligned the compass using the grid lines and your resulting compass reading will therefore be by reference to "Grid North". This is not quite the same as "True North" but the difference can be ignored.

However when you take your compass off the map it will read by reference to "Magnetic North" and so your bearing will be slightly inaccurate.

Therefore before walking off in the direction of the compass bearing you need to adjust from "Grid North" to "Magnetic North".

To do that look at the information section on your map which will tell you the "magnetic variation" for that area. If your map is not a recent one you should update the "variation" using the information printed on the map.

Having determined the "variation" adjust your compass bearing. For example the "variation" in the UK Lake District is about 4 degrees. If your compass bearing off the map is reading say 154 degrees turn the compass housing to add 4 degrees to obtain a magnetic bearing of 158 degrees.

In some countries you may need to deduct the variation so check your map!

Also in some areas the type of underlying rock formation may affect your compass and whilst this phenomonen is quite rare a little reading up on the area you intend to walk in should reveal any such problems.

If you are following a distinct path - taking a bearing for a short leg of the walk and then adjusting for the magnetic variation is not critical but it will be at path junctions and in mist or at night and for longer distances.

For more information on compass bearings go to How to use a Compass.


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