One thing that many people don’t realise when they’re new to outdoor walking and navigation is that their compass doesn’t point to grid north – except by coincidence in some areas. The compass needle is attracted by magnetic force, which varies in different parts of the world and is constantly changing.
The magnetic variation throughout Great Britain has been a few degrees West of grid North with the amount of variation changing every year. For years the number has decreased, and now in the far South West of Britain, the North on your compass lies to the East of the North on your map for the first time since before the Ordnance Survey came into existence (in 1791 if you’re interested). The change is slowly crossing the country, but for now can only be appreciated in our Custom Made maps with a centre to the West of Penzance. Buy one now and you will find a new icon we have created in the legend to show the new relationship between the three Norths (magnetic, grid and true).
We show magnetic north on all of our maps (and state the date it was calculated), but for now only Custom Made will be showing the latest figures, which we obtain from the British Geological Survey (BGS) each year.
How to use a compass:
Decide on the route of your walk and identify your starting point on the map. Place your compass on the map. Make sure the ‘direction of travel arrow’ is pointing in the direction of your route across the map. The easiest way to line the arrow is to place the side of the base plate so it crosses your starting point and the next destination of your journey.
Carefully holding the compass base plate still, you will need to turn the compass housing so the orientating lines match up with the eastings (the vertical, north–south lines) on your map. Holding the map flat and the compass still, you need to rotate your body so that the compass needle settles in line (opposite) with the index line. To fully orientate your map you will need to make some adjustments for magnetic variation.
You can properly orientate the map by carefully turning the compass housing 4º clockwise (for example, depending on where you are in Great Britain and by checking on your map legend) and then turning your body again to realign the magnetic needle with the index line. Your map is now oriented to the north.
Find out more about map reading skills with our Map reading made easy leaflet.