magnetic north setting and compass bearing

[Guest metro]

Forgive me if this has been already asked and answered, but I usually leave my etrex set for magnetic north and shoot a compass bearing when I am about a hundred feet from the cache site. If I set the my etrex to true north to aid in map settings will my compass bearing still be true?

[Guest robanna]

by the time you get to within 100 feet the difference between true and magnetic north will vary so little that it probally will not make difference. You may be off by 1 or two feet if that much.

 

PS- I find that 100 feet is almost too close to start using the compass. 150-250 is better.

[Guest fairbank]

That depends on the magnetic variation in your area. Where I live, it's 11°W and from 100' away, while I haven't done the math, that would put me way more than a couple feet off. OK, I just did the math, 19.4 feet.

 

Eric

[Guest BigFig]

And, don't forget - if you are using older maps magnetic variance changes over time and can be significant over the course of decades.

[Guest metro]

Ok folks, tell me what you suggest. In my cache searches locally I don't need to use topo maps and I only use the mapblast to get me near the cache site. I always use my compass between 200 and 100 feet and then use the etrex to estimate how close I am to the cache site. Maybe I should just experiment with magnetic north and true north and see which routinely is more accurate. Maybe there is no real difference for the narrow distance I am discussing.

 

Bill

[Guest fairbank]

It's not an accuracy issue, it's just a matter of personal preference. Do you want to work with true bearings or magnetic? As long as you apply the correct variation properly, you can use either one. I prefer to work with true. Just do it both ways and decide for yourself which way you prefer.

 

Eric