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New Techniques & Learning / Re: Magnetic Variation
« on: January 28, 2014, 01:44:25 PM »
In the main Hugh, I agree with you and do likewise. Only difference is that I do like mnemonics and find them extremely useful.
In respect of being accurate to a couple of degrees of heading on a short leg. It is not really here nor there. Practical realities vs theory; does it make a difference? To illustrate - the difference between a pure mathematician and an applied mathematician. Something you desire is 2 meters in front of you. To reach it you step forward, each step halving the distance between you and the object - 1 metre. 0.5 metre. 0.25 metre - you get the picture. How many steps do you have to take to reach the object. Pure mathematician will says you will never reach it, applied mathematician says about 8 for all practical purposes.
So it is with being 2 deg out on a 500 metre leg. Using the 1 in 60 rule which states that for every degree off heading you are then you will be l metre out of position for every 60 travelled. So 2 deg mis-heading over 500 metres = 16.7 meters out of position. Assuming of course you are able to walk in a dead straight line in the first place.
Any way when following a compass heading are we not taught to stop every few metres to check position on desired track etc and adjust accordingly. The lower the visibility / the more dodgy the terrain the more frequently we should check.
Putting 16 metres into perspective, by my estimation that is about the width of one carriageway of a 3 lane motorway.
In respect of being accurate to a couple of degrees of heading on a short leg. It is not really here nor there. Practical realities vs theory; does it make a difference? To illustrate - the difference between a pure mathematician and an applied mathematician. Something you desire is 2 meters in front of you. To reach it you step forward, each step halving the distance between you and the object - 1 metre. 0.5 metre. 0.25 metre - you get the picture. How many steps do you have to take to reach the object. Pure mathematician will says you will never reach it, applied mathematician says about 8 for all practical purposes.
So it is with being 2 deg out on a 500 metre leg. Using the 1 in 60 rule which states that for every degree off heading you are then you will be l metre out of position for every 60 travelled. So 2 deg mis-heading over 500 metres = 16.7 meters out of position. Assuming of course you are able to walk in a dead straight line in the first place.
Any way when following a compass heading are we not taught to stop every few metres to check position on desired track etc and adjust accordingly. The lower the visibility / the more dodgy the terrain the more frequently we should check.
Putting 16 metres into perspective, by my estimation that is about the width of one carriageway of a 3 lane motorway.