Thanks for the tips, Grady! They're very useful. I'm looking seriously into Trunord.

It is easy to reverse the reversed polarity and does no harm to the compass. Reversing happens all the time, you should always check daily before starting out.

There are plenty of instructions on the internet, basicly hold a powerful magnet close to the needle the correct way round which is the trick.

Now you tell me. I was planning to go to Mexico to get some relief from this winter weather, and now I'm in Yukon.

Great info Grady, thank you.



I do this with every compass I have with me on a given trip. In an area where I know north's direction, I give each compass a quick check to ensure it hasn't reversed.

Alright, I found this (from <http://cse.ssl.berkeley.edu/segwayed/lessons/exploring_magnetism/exploring_magnetism/s1.html>):



This last part about making sure the needle does not move may be a problem for a compass one cannot open, such as a keychain compass. I'll try to hold the compass vertically so as to immobilize the needle against the side. The instructions above say to hold the needle horizontally, but I don't think that's significant. We're just reversing the polarity on the magnetic field of the needle. We don't have to line up the needle with the earth's magnetic field. Will let you know the outcome. May still buy the Tru Nord.

That sounds like a heck of a lot of trouble just to avoid adding and subtracting. Especially since those compass cards are only marked with the cardinal and ordinal directions to begin with.

With all other small keychain or zipper pull compasses, you're just eyeballing or roughly guesstimating when making declination adjustments - which can cause errors of 2 or 3 degrees or even 5 or more degrees (and then you're lucky if they ever find your body). Single degree markers don't appear on keychain or zipper pull compasses. (At least I can't see them with my eyes, and I'm near sighted to a fault). Much easier just to eliminate that issue entirely on my projects where time is of the essence and/or there are immense safety concerns and particularly in remote, hostile areas and where capability, language or translation barriers run rampant for starters. All we need and all we want is a simple small rugged high quality compass with one big, clown-sized arrow (did I say big arrow and universally simplistic?) that always points in a single (one) direction, that being true north. Of course my clients use the most sophisticated cutting edge engineering and geophysical programs with ultra-high resolution imagery during other project phases, but there is a consensus among the geophysicists and engineers that understand my responsibilities, that the Tru-Nord compass is the one. Door step delivery doesn't register as an issue. In regard to direction and distance, I wear lots of hats. But I do more than my share of coordinate system troubleshooting for others. I presently use ArcInfo (formerly used GeoMedia - and I stated out in MicroStation during the civil war). My systems are loaded or are streaming with practically every conceivable type of geo-referenced raster and vector surface and subsurface data imaginable (i.e. that's out there) for reference and contrast, whether proprietary or acquired through public sources. My people are generally the first in. I agree that it's ironic that we use such a low tech tool for such critically important work in one of the most high tech environments of them all. Restated: If you need a zipper pull compass, and care about your employees, I recommend the factory compensated Tru-Nord 150C zipper pull one.

Grady,

What is you source for your compasses.

Great info too, thanks a bunch.

Blake

www.outdoorquest.blogspot.com

Tru-Nord compasses sound intriguing, and I looked up the company's website - I was glad to find they are located in Brainerd, MN, one of my favorite places. Their compensating service is certainly novel.

However, my compass use ranges across a fair variety of zip codes, usually in the western US,and I find a baseplate compass,like the Suunto MC-2 works very well. I can easily set the declination for any location quickly and easily. I can also easily determine the setting at any time (I usually leave it pointing to magnetic North,but that varies with the locality and the task). Included with the compass is a clinometer, inch and centimeter scales, a backup signal mirror, and a small magnifying lens. I have found it adequate for making sketch maps (usually of archaeological sites), as well as the all important task of finding my way back home. If I am using it, it hangs on a lanyard around my neck; otherwise, it is tucked inside the pack where it doesn't get banged around. I use a GPS a lot, but I like keeping a compass handy, even if it is not in constant use. When you need it , you really need it.

I have a Casio watch with electronic compass, which I use like that. Actually I have a poor sense of direction, so if, for example, the tour bus parks on the east side of a market square, my watch makes me more confident I can find it again. For proper navigation I'd take a proper compass (and GPS); the advantage of a watch is I always have it on me. (I used to carry a button compass, and now I don't have to.)

I trust my watch more than I do my phone. That said, I was quite impressed at how well my phone did on my last holiday. I have a dedicated GPS unit which I trust most, but it didn't have local maps, which the phone could get via free hotel WiFi. A compass would probably be better if I was stuck in a building during a power cut.

One test of a magnetic compass is to turn it on its side so the needle can't spin, then rotate it, and return it to level so the needle is pointing south, and see how long it takes find its way north again.