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Thread: Will compass work in Southern Hemisphere?

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    Member Highcomm's Avatar
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    Will compass work in Southern Hemisphere?

    My wife and I will be going to Patagonia next week for ten days. From there we go to Antarctica for three weeks. Will be doing some hiking but just day stuff. Here is a question for all of you as I can't seem to find a straight answer on the Internet - does a compass work in the southern hemisphere? Will the magnetic needle still point north? This is not a huge issue for me but just wondering. Thanks for your help!
    Last edited by Highcomm; 02-03-2013 at 01:30 PM.

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    Senior Member vegematic's Avatar
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    Yep, it should work.
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    Senior Member Nessmuk's Avatar
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    Quote Originally Posted by Highcomm View Post
    Will the magnetic needle still point north? This is not a huge issue for me but just wondering. Thanks for your help!
    Of course. North is north and south is south wherever you are on the planet. HOWEVER... there is such a thing as magnetic field DIP. Your compass needle aligns itself to be parallel to magnetic field lines. But if you recall from grade school study of magnetism, remember how those iron filings line up on the bar magnet. Near the poles (north or south), the field lines are nearly vertical. Near the mid point (equator), the lines are nearly parallel to the surface. There is information on this on this web page.

    Your compass neeedle behaves the same way. It must be slightly weighted on one end to keep it level, to compensate for the magnetic dip. If not, the needle will want to align itself with the magnetic field, which could cause it to strike the bottom of the case, depending on where you are on the planet. The balance weight is the opposite in opposite hemispheres. When you buy a compass in North America, it may not work very well in Patagonia because the needle balance is wrong. You have to either buy a compass balanced for dip in South America, or you can now buy what is known as a universal or global compass such as the Suunto MC-2G (G for Global) , which is supposed to work everywhere by the mechanism built in.
    Last edited by Nessmuk; 02-04-2013 at 05:19 PM.
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    Senior Member DougPaul's Avatar
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    Depends on the model--check the documentation for your model. Many compasses are designed to work in a specific zone, global compasses are designed to work world-wide. See HH1's link for the zones and a description of the global compass.

    The problem is caused by the vertical component of the Earth's magnetic field--it can cause the needle to tilt such that the needle or the bearing hits or rubs on something. The zone compasses can only tolerate the vertical forces over part of the earth and the global forces can tolerate the forces anywhere.

    No magnetic compass is of much use near either of the magnetic poles, however the southern magnetic pole is currently located just offshore of Antarctica toward Australia. Thus your compass should be ok in Patagonia if works in that zone. Make sure you use the correct declination for your location.

    Doug

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    Senior Member Ed'n Lauky's Avatar
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    This is an interesting discussion. I was wondering what the effect in changing hemisphere would be on a 3 axis electronic compass such as is found in my GPSr.
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    When I went to New Zealand a few years ago I pulled out my trusty Sunnto plate compass and I could not use it as the needle dipped and hit the case of the compass. I didnt need it but it was at rouhgly the same latitude as the whites.

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    Senior Member DougPaul's Avatar
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    Quote Originally Posted by Ed'n Lauky View Post
    This is an interesting discussion. I was wondering what the effect in changing hemisphere would be on a 3 axis electronic compass such as is found in my GPSr.
    The problem is mechanical--3 axis electronic compasses should be ok (assuming their software is written properly).

    Doug
    Last edited by DougPaul; 02-03-2013 at 06:44 PM.

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    Member Highcomm's Avatar
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    Many thanks for the feedback. I've ordered a Suunto MC-2G compass and will bring that. Will also bring my standard compass. I'll also test the compass on my iPhone. I'll report back later in March how everything compared.

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    Senior Member Jazzbo's Avatar
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    Quote Originally Posted by Nessmuk View Post
    Of course. North is north and south is south wherever you are on the planet. HOWEVER... there is such a thing as magnetic field DIP. Your compass needle aligns itself to be parallel to magnetic field lines. But if you recall from grade school study of magnetism, remember how those iron filings line up on the bar magnet. Near the poles (north or south), the field lines are nearly vertical. Near the mid point (equator), the lines are nearly parallel to the surface. There is information on this on this web page.

    Your compass neeedle behaves the same way. It must be slightly weighted on one end to keep it level, to compensate for the magnetic dip. If not, the needle will want to align itself with the magnetic field, which could cause it to strike the bottom of the case, depending on where you are on the planet. The balance weight is the opposite in opposite hemispheres. When you buy a compass in North America, it may not work very well in Patagonia because the needle balance is wrong. You have to either buy a compass balanced for dip in South America, or you can now buy what is known as a universal or global compass such as the Suunto MC-2G (G for Global) , which is supposed to work everywhere by the mechanism built in.
    Wow! What a great insight this little tidbit gives! I wonder if back in the days of the arctic explorers if they were able to adapt their compasses or developed new devices to locate the poles. I must look this up on Google soon.
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    Junior Member Jackel's Avatar
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    Really interesting question and thread. Thanks for the info!

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    Banned Kevin Rooney's Avatar
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    When I go to Patagonia and Antarctica I'll just bring my Garmin 60CSx.

    Next question?

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    Senior Member Nessmuk's Avatar
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    Quote Originally Posted by Kevin Rooney View Post
    When I go to Patagonia and Antarctica I'll just bring my Garmin 60CSx.

    Next question?
    How many batteries will you bring?

    When flying over the pole in the Air Force back in the day, I used a sextant and a clock (really). Two compasses were slaved to gyros that were kept updated by sextant sightings when declination was off the charts. Inertial nav systems in a foot locker size box were rare and too new - often unreliable and accumulated errors with time. GPS did not yet exist. But the stars sun and moon, ah yes, I could always count on them with manual calculations and "sight reduction tables". Such a lost art. Pity.
    Last edited by Nessmuk; 02-05-2013 at 04:50 PM.
    "She's all my fancy painted her, she's lovely, she is light. She waltzes on the waves by day and rests with me at night." - Nessmuk, Forest and Stream, July 21, 1880 [of the Wood Drake Canoe built for him by Rushton]

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    Banned Kevin Rooney's Avatar
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    Quote Originally Posted by Nessmuk View Post
    ...When flying over the pole in the Air Force back in the day, I used a sextant and a clock (really). Two compasses were slaved to gyros that were kept updated by sextant sightings when declination was off the charts. Inertial nav systems in a foot locker size box were rare and too new - often unreliable and accumulated errors with time. GPS did not yet exist. But the stars sun and moon, ah yes, I could always count on them with manual calculations and "sight reduction tables". Such a lost art. Pity.
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    Senior Member DougPaul's Avatar
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    Quote Originally Posted by Kevin Rooney View Post
    When I go to Patagonia and Antarctica I'll just bring my Garmin 60CSx.
    Quote Originally Posted by Nessmuk View Post
    How many batteries will you bring?
    Reinhold Messner and Arved Fuchs walked and skied from the coast to the geographical South Pole and back to the coast using a GPS for navigation in 1989-1990. (The GPS constellation was not yet complete--they may have had to wait for some fixes.)

    I don't know how well a 60CSx will handle Antarctic temps (it is only rated to 5F) --perhaps a ruggedized unit would be required.

    Batteries last a long time if you only turn the GPS on for a few minutes every day or few days.

    Doug

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