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Guest skyboy

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I use true. I set the mag. dev. on my compass so I can use true on it also. As long as everything you use is set the same it shouldn't matter. When I try and do the deviation in my head I usually screw it up. (Never did get the meaning of "east is least and west is best"... icon_smile.gif

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I use true. I set the mag. dev. on my compass so I can use true on it also. As long as everything you use is set the same it shouldn't matter. When I try and do the deviation in my head I usually screw it up. (Never did get the meaning of "east is least and west is best"... icon_smile.gif

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True north allows you to use a map without doing any calculations.

 

Depending on your location in the world there can be huge differences between magnetic and true north, or none at all.

 

Maps use true north, so if you're using one it'd be easier to navigate if you have an electronic compass that can calculate true north.

 

Jeremy

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Then it sounds like I made a good decision. I chose True north.

Its been a while since I taught the Orienteering Merit badge but isnt our declination here in UT somewhere around 12-17 degrees?

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Guest CaptainCurmudgeon

>>declination here in UT somewhere around 12-17 degrees?<<

 

Yep, although most of the state is between 13 and 16.

 

But hell^h^hck, everyone in Utah can find true N/S E/W -- it's the way every street in every city, town, and village runs.

 

[Of interest to Utahns only: I think we can thank Orson Pratt for that.]

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Guest Ciemon Dunville

quote:
Originally posted by jeremy:

True north allows you to use a map without doing any calculations.

 

Depending on your location in the world there can be huge differences between magnetic and true north, or none at all.

 

Maps use true north, so if you're using one it'd be easier to navigate if you have an electronic compass that can calculate true north.

 

Jeremy


 

That's not true Jeremy... some maps don't use UTM as a base (which uses true north). In the UK, the Ordnance Survey of Great Britain based the grid on one that follows the line of the country a bit better. Consequently, in the UK we have grid, true and magnetic north!!

 

So the way it generally works here is to use magnetic North on your compass and do a "Grid to Mag add, Mag to Grid get rid" calc depending on whether your going from map to compass or vice-versa.

 

Confusing eh!

 

Ciemon Dunville

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Guest swangner

For geocaching, anyway, I set to True North. I'm not really using my magnetic compass until I get close (within 200 feet or so) of the cache anyway, and with distances that small, the difference between magnetic and true north are almost negligable.

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Well, call me silly doing it the way everyone else DOESN'T, but I leave my Garmin set to auto magnetic variation. The isogonic data in the Garmin is pretty accurate, so I can count on a good mag bearing. No need to adjust my compass, either, although my compass allows it. In geocaching, I seldom find the need to get map bearings, since the GPS is telling me everything I need to know. I only carry the map as a reference to the landforms (which hill is steeper, etc.)

 

Scott

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to agree with ScottJ. Auto magnetic variation. My compass does not let me compesate for variation so I just let the GPS do it for me. I rarely use maps while geocaching but I do take one with me just in case.

 

Matt

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I've discovered I'm "bi"! icon_wink.gif If I'm using a paper map (rarely when geocaching) I set the GPS to true and adjust the compass.

 

If I don't use the paper map I set the GPS to mag. and set the compass to zero declination. So far it works well either way.

 

-scott

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I've discovered I'm "bi"! icon_wink.gif If I'm using a paper map (rarely when geocaching) I set the GPS to true and adjust the compass.

 

If I don't use the paper map I set the GPS to mag. and set the compass to zero declination. So far it works well either way.

 

-scott

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Guest fairbank

Ciemon Dunville wrote:

>That's not true Jeremy... some maps don't >use UTM as a base (which uses true north). >In the UK, the Ordnance Survey of Great >Britain based the grid on one that follows >the line of the country a bit better. >Consequently, in the UK we have grid, true >and magnetic north!!

 

Only the UTM grid line at 500.000km (center of a zone) points to true north. All other grid lines point to grid north which can be up to 2 degrees in the U.S. Look on the bottom of any USGS topo map and you will find the declination for magnetic north and grid north. These maps are old so never use the magnetic declination from them.

 

Eric

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