Can the cubs work out the grid magnetic angle by themselves? If they can't grasp the concept that magnetic north is moving eastwards every year then I'd stay away from magnetic declination for a while.
Setting a compass
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Not sure I would talk about mag declination at all to be honest. As the others have said, it's a bit complex for them and could just end up with them confused. Plus you have to remember, that in the UK the declination is only between 2.5 and 1.5 degrees (and getting smaller), it really isnt worth bothering with (here). The other issue is that map reading is really about relating the map to the land. If you can see landmarks in your environment and can relate them to the map, then you know where you are and dont need a compass - you only need a compass for orientating yourself and the map to the land - and you can do that just as well by looking for the mossy side of a tree, or looking at the way the sun is moving - and that is prolly tons more fun for cubs. Get em used to reading the land and relating what they see to the map, landmarks, contour lines, rivers, buildings etc. A good solid basis in that will underpin complex compass work if they later want to attempt things like navigating featureless landscapes in the dark.
Teaching them to navigate without a compass, is probably the best gift you could give them. If you really must do compass work, I'd stick to the Silva 123 method and teach em nowt else at all.
...and for your own reference, as said above, declination is "grid to mag add, mag to grid get rid" - for the northern hemisphere and the opposite for the southern hemisphere.
Teaching them to navigate without a compass, is probably the best gift you could give them. If you really must do compass work, I'd stick to the Silva 123 method and teach em nowt else at all.
...and for your own reference, as said above, declination is "grid to mag add, mag to grid get rid" - for the northern hemisphere and the opposite for the southern hemisphere.
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To preserve my sanity I've just finished the grid into which they place their answers, and d'ya know, I've filled in several of them...as examples of course! I'll report back how it went.
might set up a very simple orienteering course, put a paper on the back of each target tree with the heading towards the next tree/number of paces
That's a great idea. You could make a little competition out of it. Send em off in pairs out of sight and sound of the others and time em round a course. Maybe the fastest pair round could win a compass or a badge or something?
I wouldn't even contemplate talking about magnetic variation at that level, far too complexed for the age group and will probably just confuse them, keep it simple mate.
A good resource is the (NNAS) National Navigation Awards Scheme, the syllabus listed will give you an idea what to be covering with young people and adults of all ages and abilities.
Here's a link......
http://www.nnas.org.uk/
A good resource is the (NNAS) National Navigation Awards Scheme, the syllabus listed will give you an idea what to be covering with young people and adults of all ages and abilities.
Here's a link......
http://www.nnas.org.uk/
After taking into account the above posts I think it was pitched about right last night. I just mentioned mag variation and one Cub came up afterwards to ask more.
Ripon is 2deg 39sec West of true north
3deg 01sec West of Mag North
Grid is 0deg 23sec East of true north.
For magnetic variation you can use the following calculater at the british geological survey website...you can enter your location in a number of formats even postcode, it is updated every year and if you look at a os map the magnetic data is supplied by the survey
http://www.geomag.bgs.ac.uk/gifs/gma_calc.html
Regards
stu
http://www.geomag.bgs.ac.uk/gifs/gma_calc.html
Regards
stu
Variation east, compass reads least,
Variation west, compass reads best.
The same is true for other compass errors. For example if you have magnetic materials near to the compass (such as in a steel boat) you can have a 'deviation' which may not be constant. So instead of the rhyme above you can just say
Error east, compass least,
Error west, compass best.
where error = deviation + variation + AnyOtherErrorsYouCanThinkOf.
Some people use the term 'declination' instead of 'variation' but I tend to think of declination as relating the vertical component of the magnetic field, which doesn't really affect you unless you're sailing a steel boat on its ear. Then you can get a 'heeling error'. It's just another error.
There's a great book by Mary Blewitt which covers this stuff. There are some that go into it quite a bit deeper, but I think that's probably more than enough for the cubs.
Variation west, compass reads best.
The same is true for other compass errors. For example if you have magnetic materials near to the compass (such as in a steel boat) you can have a 'deviation' which may not be constant. So instead of the rhyme above you can just say
Error east, compass least,
Error west, compass best.
where error = deviation + variation + AnyOtherErrorsYouCanThinkOf.
Some people use the term 'declination' instead of 'variation' but I tend to think of declination as relating the vertical component of the magnetic field, which doesn't really affect you unless you're sailing a steel boat on its ear. Then you can get a 'heeling error'. It's just another error.
There's a great book by Mary Blewitt which covers this stuff. There are some that go into it quite a bit deeper, but I think that's probably more than enough for the cubs.
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