Help on compass stuff

Ok so I have my charity walk, have marked all the points on my map and am ready to go....nearly.
Think I understand following a bearing, triangulation and stuff but.....do I need to add or take away a few degrees from each of the clues to account for magnetic north or whatever it is??? Can't quite get my head around it. If only it was cheap to buy an etrex

do I need to add or take away a few degrees from each of the clues to account for magnetic north or whatever it is??? Can't quite get my head around it.

Hi Bog Baby. OK. It took me some time to get my head around it too. There are three Norths in the UK. From West to East, they are: Magnetic, Grid and True. The gap between True North and Grid is about 2 degrees and is printed on all OS map legends. Helpfully (!), the magnetic one differs all over the world, and changes unpredictably, and its this one which affects you, your compass, and your walk plotting.

Currently, and based on the British Geological Survey's Grid Magnetic Angle Calculator:(http://www.geomag.bgs.ac.uk/data_servic ... _calc.html)
Magnetic North on Dartmoor is 0 deg 41 minutes WEST of Grid North, and decreasing at about 11 minutes a year. There are 60 minutes in a degree so based on this, all our bearings are about half a degree away from parity - Magnetic and Grid Norths aligned (which has already occurred in West Cornwall)

To be as precise as can be, when you convert a clue or physical, visible bearing and apply it to the map, you'll need to TAKE OFF, or get RID of 0.5deg. When converting a bearing on the map to reality, you'll need to ADD 0.5deg.

I used to take the physical act of bending down to the map as my cue to remove degrees.

The saying: 'Mag to Grid, get rid. Grid to Mag, add' is a Boy Scout Navigational Mantra, and is worth remembering (for the next 4 years at least!)

Hope this helps

If only it was cheap to buy an etrex Laughing

NEW Garmin etrex for £59.88 with free delivery.

http://www.handtec.co.uk/garmin-etrex-h ... wwod1XYAIw

Whoisthechallenger is right, if you want to use the bearings given to plot the locations of the boxes on the map, very precisely, before you set out. But it would be easier to use the grid references given with the clues and the handy scales on the base plate of your compass. That saves drawing lines all over your map.

When it comes to actually finding the boxes, then you do not need to worry about variation. All the clues for the charity walks are recent, so the earth's magnetic field will not have had any time to vary since they were done. Just use the bearings as they are given in the clue when lining up your compass.

Good luck!

Fabulous thank you for that BH and WITC, looking forward to our hike and the weather is looking good

Here's a tip for you, if you are going to plot positions on a map with a pencil
Use a 2B pencil as it can be cleanly rubbed out