Using my compass

[askew116]

As some of you may have read from my previous post, I'm from the UK, and later this year will be embarking on an end-to-end bushwalk of the AAWT.

I came across some very old posts on this forum, but thought it better to start a new thread in case the OP were no longer active:

The thread stated that a compass bought in one hemisphere will not work correctly when used in the other hemisphere. So, I've bought a Silva compass in the UK, and I need to know if it will work correctly in Australia? My gut instinct is that if a compass points towards magnetic north, it should do so regardless of which hemisphere you're in, but obviously not having prior knowledge of the area, I don't want to risk ending up with an unreliable compass.

Can anyone shed any light on this?

[icefest]

http://www.suunto.com/da-DK/Support/Com ... ing-zones/

[Maaxxx]

Yep! That's pretty much it. Your compass needs to be balanced for the hemisphere you're using it in.

[tom_brennan]

As above from icefest. Basically it means that the needle may not lie flat on the baseplate. One end of the needle might lean against the baseplate, and therefore the needle won't spin freely. It can still be used, and will still point north, but may need to be shaken to get the needle moving each time.

[photohiker]

There are two ways of dealing with this. Either buy a compass here in Australia when you get here, or swap the compass you just bought for one with a 'Global' needle. With a bit of luck, the place you bought your Silva from will be able to help.

A global needle compass works anywhere on the planet, it uses a needle that does not tilt to the baseplate with the angle of the magnetic field.

[neilmny]

I mistakenly bought a northern hemisphere compass a while back.
It could be used to some extent but was an absolute pain in the butt.
A hand bearing required tilting the compas to let the needle swing freely
which was ok but on a flat map say on the ground or some other horizontal
face it was useless.

[enbuyukfener]

Get two cheap compasses, that should cover most of the 5 "zones" adequately.

Alternative are global compasses, but they come in at $50+ usually. Maybe cheaper if you DIY by replacing the needle in your compass.

[thejungleisneutral]

+1 on a global compass. I use a Suunto MC-2G which is a mirror-sighting baseplate compass.

I have used modern northern hemisphere-balanced Silva compasses (Silva Expedition 4 MIL) in the past and in most areas of Australia they are a pain in the backside - too much "dip" required to use them. The compasses are quite accurate, but having to tilt them there's a danger of getting inaccurate readings if not careful, and there's always the possibility of the compass card (the needle thingy which points north) becoming hung up on the inside of the capsule on any northern hemisphere baseplate type.

Interestingly, I have used quite a few vintage compasses dating from the first half of the 20th century, which were made and used in the northern hemisphere, and there is no discernible "dip". Being brass-cased prismatic, lensatic and mirror types, however, these may be a bit heavy for a jaunt along the length of the AAWT

[durks]

... I've bought a Silva compass in the UK, and I need to know if it will work correctly in Australia? ...

As per previous posts above: the compass will work in Australia, but you'll have to angle the baseplate to get it to pivot cleanly. That does generally work, but is not ideal, and it can become a real problem when/if the compass develops a bubble: in those circumstances, the bubble can make it hard to get a valid bearing.

My recommendation: buy a 'southern hemisphere' compass in Australia when you arrive, and use that. I have two Silva Type 3 compasses (one 'MN', the other 'MS' - see the underside of the baseplate) for exactly that reason.

[GPSGuided]

That Suunto M3G review is pretty good. Buy one compass and make it globally balanced, and now I have two. Oops.

[wallwombat]

Years ago I met a solo walker in the Blue Mountains who had spent a day or so stumbling around lost because he had tripped over and broken his compass. It always made me think that if you are walking solo, it may be a good idea to pack a spare.

I often walk solo and I don't carry a spare but I rarely go anywhere that I might get lost when I'm walking alone,

Just a thought.

[madmacca]

Years ago I met a solo walker in the Blue Mountains who had spent a day or so stumbling around lost because he had tripped over and broken his compass. It always made me think that if you are walking solo, it may be a good idea to pack a spare.

I often walk solo and I don't carry a spare but I rarely go anywhere that I might get lost when I'm walking alone,

Just a thought.

As a backup, most smartphones have a digital compass onboard. You may need an app like Smartcompass to get the most out of it. Plus there is always the watch-sun method.

[icefest]

When you can't exactly see the sun, you can still use the watch-sun method by using the polarization of light through the clouds. this takes a bit of getting used to but works to a reasonable extent.

[madmacca]

As some of you may have read from my previous post, I'm from the UK, and later this year will be embarking on an end-to-end bushwalk of the AAWT.

I came across some very old posts on this forum, but thought it better to start a new thread in case the OP were no longer active:

The thread stated that a compass bought in one hemisphere will not work correctly when used in the other hemisphere. So, I've bought a Silva compass in the UK, and I need to know if it will work correctly in Australia? My gut instinct is that if a compass points towards magnetic north, it should do so regardless of which hemisphere you're in, but obviously not having prior knowledge of the area, I don't want to risk ending up with an unreliable compass.

Can anyone shed any light on this?

As others have said, the compass will still point north but may 'stick' due to the needle being incorrectly balanced for the southern hemisphere. Tilting it should allow the needle to swing freely.

While there are many places where you need to confirm the broad direction (eg. take care to follow the NW spur), there are only about 1 or 2 places on the entire AAWT where you need to shoot a precise bearing. The tilt method with a N. Hemisphere compass is quite workable for these odd occasions. If you were having to follow compass bearings for extended distances in featureless terrain, then a global or zone-specific compass would be more worthwhile. For the AAWT, I'd just be aware of the issue, and save my money.

[Zone-5]

Silva - frequently asked questions

http://silva.se/frequently-asked-questions#11


What is inclination?
A compass will react to the Earth´s magnetic field and the compass needle will tilt (vertical direction) downward or upward depending where you are location on Earth. It means that the needle will always be parallel to the Earth´s magnetic field.
inclination:


What is Deviation?
The difference between True North (geographic North) and Magnetic North.
Magnetic deviation will occur in some places of the world, often caused by high amounts of metallic ore in the ground. This will cause the needle to divert either west or east and the deviation varies between 1 and several degrees depending on the amount of material that influence the needle at the place where you are. Most maps will have a note regarding the local magnetic deviation and on how to calibrate for it. Many of Silva’s compasses have a function to compensate for the deviation; this is very useful for avoiding mistakes.

Our balancing zones
All Silva compasses are balanced in three different zones:
MN (Magnetic North)
ME (Magnetic Equator)
MS (Magnetic South)
balancing zones:


Can I use my compass in any part of the world?
No, all Silva compasses are weighed for one of three magnetic zones and using your compass in the “wrong” zone will cause the needle to tilt and may result in it getting stuck against the roof/floor of the capsule and showing an incorrect north.

Does Silva make a compass that can be used all over the world?
No, Silva Sweden does not have a compass equipped with a so called global needle.

[Zone-5]

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