The Magnetic Compass.......

[Silverclaws2]

And so it was I recently received yet another compass purchased from a certain popular auction website, an old Recta matchbox compass from the 1970's I think, maybe a DP5, purchased primarily for interest's sake as they had been on my radar back in the day. Anyway on reading the supplied instructions that it came with I understood this compass may well have had a fluid filled capsule at one time, not there was any sign of there ever having been fluid in the compass I had just bought, to think, hmmm, maybe I should just fill it anyway to deal with that extremely slow to settle needle.

So off online I went to find out about filling compass capsules, to also come across the suggestion that it's compasses with weak magnetism that don't settle as quickly as one would like, to then go off in search of what to do with weak magnetism in compasses. To find two methods of achieving thus, a method involving a bar magnet and a method involving electro magnetism, of which to me seemed the better option, but because I had a strong bar magnet handy, I gave it a go, to find yes indeed it did improve the north pointing and settling speed even in an un-damped compass, a quite stunning improvement in fact. To then think I will just go and check this magnetic north seeking ability with one of my other compasses, to find the first one selected pointed in a different direction, to then try another to find the same and finally my decent Suunto MC-2 to find, guess what that was different too, for all of them to be indicating magnetic north to be in a different direction - AAARRRGGH

For then the thought to arrive, what if one only had one compass, to trust that one compass in the belief that it was true, when it stands compasses can lose their magnetism over time and can even be motivated to point into entirely different directions by the electro magnetic fields our twenty first century living brings. And yes for interest I did use one of compasses around my desk, to find out just what was emanating a magnetic field, for the question to then come ' how the hell can I store these potential life savers to be in a position to trust them when they're needed, to have concluded unless I bury them in the middle of a field of known geology, not much chance of that, to then think, perhaps I need to polarise the compasses before I take them out, to be in a position to put trust in them, particularly after what I have just discovered.

So for other that uses compasses, how'd you know your compass is pointing true?

 

[Robson Valley]

There's a global agency which sets the position of the North Magnetic Pole, every few years.
Most recently, they announced that the NMP is galloping westward like nothing recorded before.
So what you might read as the NMP offset on the corner of a topo map is well off the mark.

I can see Polaris from my front doorstep on any clear night.
It is directly above the Stop sign at the end of my street.
My Brunton Eclipse prototype has an offset of about 25 degrees. I forget exactly.
It has a little disk magnet which I expect to outlast my lifetime.

Outside on my doorstep, I do see the geographic North with my Brunton
and my 1965 Recta Prospector. Bubbles and all.

 

[Paul_B]

Not saying you are doing this but comparing two compasses by holding them alongside each other will allow the two to affect each other. It's probably something you know about but worth mentioning just in case. Plus there's electrical devices that can affect it as you've experienced.

 

[Robson Valley]

Find Polaris from a fixed position that you can remember. Your compass should hit this,
provided that you made the correct magnetic offset. Keep away from ferrous metals.

 

[Silverclaws2]

Not saying you are doing this but comparing two compasses by holding them alongside each other will allow the two to affect each other. It's probably something you know about but worth mentioning just in case. Plus there's electrical devices that can affect it as you've experienced.

Yeah I am aware of that, to have tested each compass one at a time in the same position and yeah I know about the electromagnetic fields in a house to have used a compass in finding them.

But anyway, I found the stroking of a bar magnet over one of the compasses, the Recta caused it to point in a different direction, to be considering seeing if my old bench power supply still works, to do this ;

Re-magnetising a navigation compass using electro magnetism

To at least know they stand more chance of being true thereafter

 

[Silverclaws2]

Find Polaris from a fixed position that you can remember. Your compass should hit this,
provided that you made the correct magnetic offset. Keep away from ferrous metals.

I understand this year, for the first time in 360 years true north and magnetic north align at the Greenwich meridian, to know the mag offset in my part of the world is currently thirteen minutes east of grid.

 

[Robson Valley]

I have no idea what the offset is for me here at 53N and about(?) 102W.
It's on all the map sheets plus a number for yearly change.
However, since it's moving so fast, none of that stuff is relevant any more.
I guessed that it all has to line up 00 - 00 for somebody!

That's OK. I don't do any more overnight stuff since it's convenient to drive home,
living in the middle of forested mountains.
It's easy to say we just look up at familiar mountain peaks
but it doesn't work that way in fog, heavy rain or snow storms that come up in 60 seconds.
My Brunton has set me right twice when I really believed that I knew my course. Wrong.

I've just bought a couple of average compasses and 8x25 porro binocs for my twin grandsons' birthday.
Wish I could travel to be with them for a day in the park.

 

[Paul_B]

@Silverclaws2
I didn't doubt that you knew that, just thought it worth saying in case others reading it didn't know. I reckon most people who are regularly on this site know more than most about navigation. I also know some of my Google searches have also given links to BCUK threads for answers to my questions. So I believe going back to the basics is worth doing.

Back to topic I've never really thought about remagnetising a compass. I've been on the feels of these lake district and felt my compass was out before. I just got another one because it's about confidence in such an important tool for the outdoors for me. Turns out the faulty and new ones were pointing north in different directions. However the faulty one ended up somehow pointing the same north as the new one after a few years in the cupboard and what I assume the correct direction too since it was checked at home where I'm able you determine north quite easily.

Could leaving the faulty compass over time cause it to somehow self correct? We're taking about 10 degrees out ending up at virtually zero degrees out.

 

[Riven]

Interesting video, my one question is how much power is needed to re-magnitise? Would a battery work and if so what voltage?

 

[Silverclaws2]

@Silverclaws2
I didn't doubt that you knew that, just thought it worth saying in case others reading it didn't know. I reckon most people who are regularly on this site know more than most about navigation. I also know some of my Google searches have also given links to BCUK threads for answers to my questions. So I believe going back to the basics is worth doing.

Back to topic I've never really thought about remagnetising a compass. I've been on the feels of these lake district and felt my compass was out before. I just got another one because it's about confidence in such an important tool for the outdoors for me. Turns out the faulty and new ones were pointing north in different directions. However the faulty one ended up somehow pointing the same north as the new one after a few years in the cupboard and what I assume the correct direction too since it was checked at home where I'm able you determine north quite easily.

Could leaving the faulty compass over time cause it to somehow self correct? We're taking about 10 degrees out ending up at virtually zero degrees out.

What I know is that magnetised things can lose their magnetism over time, for it to make sense compasses may become weaker to perhaps wander around more, to have wondered what a compass featuring a neodymium magnet would be like, I mean some compasses use the mildly radioactive gas ; tritium for luminosity, why not go supercharged with neodymium.

Anyways I feel my way forward with my compasses is to go down the electromagnet polarisation route, perhaps before taking them out to have more faith in them, and faith given what I've found out about them and yes I have seen compasses that have reversed polarity ;

https://lotsafreshair.com/2012/11/07/polar-opposites-when-compasses-go-bad/

 

[Silverclaws2]

Interesting video, my one question is how much power is needed to re-magnitise? Would a battery work and if so what voltage?

Quite, where to perhaps do what I'm going to do ; experiment with batteries before turning to plug in stuff, where of course if one can with a battery make a usable electromagnet to polarise a compass, that could form a useful in field aid.

http://www.schoolphysics.co.uk/age1...netism/text/Electromagnet_polarity/index.html

 

[Crowe]

Stronger magnetism in a compass needle can lead to 'dip'. Look up compasses for northern and southern hemisphere. Always a good idea to check your compass function and variation against a 'transit' line(East /West) and true north(polar, North star). As @John Fenna and others mention.
Magnetic anomalies and compass errors can really spoil your day

 

[Robson Valley]

At the time, I didn't know that my old 1964 Recta had a needle balanced for the northern hemisphere. 1969 and I find myself on a trek into the outback, the Snowy Mountains to precise, in Oz. I had to point the compass 45 degrees to the ground to get the needle to float. But, it did read true enough.

A bubble developed and years later, I bought a Brunton Eclipse prototype on the very best of advice. Now, they are made with button magnets for either hemisphere AND one for global use.
The OP can't remember to add sudden mountain snowstorms when the visibility sinks to 20 yards or less in seconds. That was an experience. So the deal is: let's go back to camp, get a fire going and nibble on stuff until dark drives us into bed.

I apologize to all. I keep forgetting that the compass is a very foreign object to many people. I took it for granted that every kid had one and read maps.

 

[ged3]

... So for other that uses compasses, how'd you know your compass is pointing true?

You're making measurements. If nothing else as an engineer, I'm a measurements man.

If the magnetic field lines that were applied to the needle were even a few degrees off the line of the needle you could expect at least that much error after you applied the magnetizing field. If you tried not particularly hard I'm sure you could make the needle point east-west.

I'm not sure that I'd want to try to (re-)magentize a compass needle without first taking it out of the compass body so that I could be certain that the lines of magnetic field that I applied to it were as closely parallel to the needle itself as I could possibly make them. I've never been convinced that it's easy (or even possible) to do that when the compass is completely assembled and the needle is free to move. Don't forget that all magnetic field lines are three-dimensional. Theoretically you can make the needle have a magnetic field which points up and down as well as left and right. In fact theoretically it will be difficult not to. You might have a grip on that, but there's very little that you can do about the Earth's magnetic field which in the UK at least at the moment points down at a little under 70 degrees to the horizontal. Yes, you read that right, seventy degrees. So it's pointing down a lot more than it's pointing north, and as a result you'll need to be a lot more careful with the up/down field inclination that you apply to the needle than you will with the left/right field inclination.

Magnetic dip - Wikipedia

en.wikipedia.org

Magnetic compasses made by people who are more serious about their work are made for particular areas on the planet. The product will come with a certificate which says so. Yacht compasses have to (try to) take account of dip, because a yacht heels when it sails and that can make the compass point very significantly left or right of where it would point when the boat is upright. They keep a card which gives offets from the true value for a number of headings, and interpolate at headings between. They have to make adjustments if they go on long passages. They have to recalibrate after lying in dock for any length of time. They could of course simply rely on GPS but that would be asking for it. I'm not saying I've never done it.

I believe it was Confucius who said, "Man with watch knows what time it is; man with two watches never really sure". That's of course taking things to absurdity, but you will never get two compasses to point in exactly the same direction. You need to take a view on what's acceptable, and that depends on what you're doing at the time. I'd, er, be over the moon if I could get within five degrees every time.

Please note that the pole star describes a daily circle around the north pole about 1.5 degrees in diameter. For accurate work you need to correct for that. At the moment the circle is getting smaller year on year. I guess I won't live to see it reach the minimum of just under a degree in 80 years' time (February 2102).

For more than you ever really wanted to know about finding directions I can recommend the book "Emergency Navigation" by David Burch. Apart from brief correspondence many years ago I have no connection with the author, I'm just a satisfied owner of two copies - the original two-volume version and the later single volume:

Emergency Navigation second edition by David Burch $13.95 ISBN 9780071481847

This book isn't the Compass Bible, if there is such a thing, but I've used the knowledge in it to save my own bacon on what could loosely be described as "land". On that occasion there were no instruments at all other than my own senses.

Heck, I only opened this account to try to find if there's a meet near Clay Cross this weekend because I couldn't get the forum software to send mail to me at my old address. :/

 

[knowledge=gain]

Yeah I am aware of that, to have tested each compass one at a time in the same position and yeah I know about the electromagnetic fields in a house to have used a compass in finding them.

But anyway, I found the stroking of a bar magnet over one of the compasses, the Recta caused it to point in a different direction, to be considering seeing if my old bench power supply still works, to do this ;

Re-magnetising a navigation compass using electro magnetism

To at least know they stand more chance of being true thereafter

here is a much simpler and quicker way that does not need any wires