Many of our customers use a map and compass and are involved in many outdoor activties. I know even while out canoeing it is a handy skill.
But a lot of users don't realise there is a difference between grid north (those blue lines on the map) and magnetic north (where your compass points).
The reason for the post is that after years of teaching navigation, that now anywhere West of Penzance I can no longer use these easy rhymes to teach bearings;
map to grid -> add
grid to map -> subtract.
Essentially to make sure your navigation was spot on, you had to adjust your compass when taking a bearing from the map or if you were taking a bearing off the land. If you took a bearing on land - say to the corner of a cliff or to an island on a lake - you would then need to subtract some degrees to line up the bearing on your map and vice versa.
The opposite is now true in places further West than Penzance - as Ordnance Survey announced on their blog -
'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).'
Summed up -Magnetic North and grid North align at Penzance rather than off the mainland so you have to adjust your compass accordingly. (@coldfunk on Twitter- cheers)
I'd recommend getting on an outdoor course and learning some simple navigation skills - even to extend your trips just a little further off the beaten track. Every year we organise the Big Shakeout and we have had a number of navigation courses there to try. Alternatively grab the 'Ultimate Navigation Manual' from our store and do some reading - it's the best book we've found.