The problem with large variation numbers is that they aren't consistent, very local and then it's back to normal but you don't know it's back to normal and you're still trying to figure out how far off the compass is from where it should be.

A bit of celestial knowledge can be a god-send.

Yes indeed! In the case I mentioned, we had started before dawn on an ascent of Orizaba, the tallest of the Mexican volcanoes. My companion was navigating with his compass. It was a beautiful night and I had Polaris in sight,so we got straight quickly. The considerable variation was probbly due to iron in the surrounding lava flows.

Give me a starry night any day....

I've been following this thread with some interest. Here are some thoughts:

Need for a compass: Like hikermor and others, I find most of the time I don't really need a compass or GPS (although I always carry both). I spend most of my time in fairly rugged terrain, and just using my Mk I Eyeballs and associating terrain to map is all I need. However, as has been noted, in certain situations (relatively featureless terrain, poor visibility, etc) a compass is needed. I don't often need a compass, but when I need it, I need it bad!

Bubbles: Annoying, but unless they get rather large they aren't a big deal. It is usually fairly obvious when a bubble is big enough to interfere with the needle.

Compass in cold weather: Awhile back some of us were doing a navigation exercise in chilly weather. It was about +3 deg F (-16 C). Several people's compasses (all Suunto's as I recall) more or less stopped working! What seemed to be the cause is that the oil filling was getting so viscous that the needle could no longer move freely. My Brunton (Type 15) developed a bubble, but kept working. When they warmed back up the Suunto's started working again, and the bubble completely disappeared from my Brunton. Since in Alaska it does get cold now and then, a bubble is annoying, but a needle that doesn't move at all is unacceptable!

Awhile back I heard about the German made K&R compasses, which I believe someone else mentioned up thread. They might be the ticket for cold weather use. I recently ordered a K&R Alpin Sighting Compass. When I get it and get a chance to use it, I will post a report.

Accuracy with a handheld compass: Using a decent mirror sighting compass, you should be able to get withing 2 deg, plus or minus, if you are careful. This is adequate for most uses. I don't much care for lensatic compasses (though I confess I haven't a lot of experience with them). If you need better than 2 deg, I would go with a Brunton Pocket Transit. I've used them doing geologic fieldwork and they are an awesome instrument, but they are big, heavy, clunky, and cost $400-$600.

Declination and old maps: I would never rely on the declination posted on a map margin unless it was a really newly published map. Here around Anchorage Alaska, declination changes by about .34 deg/year. That means that the declination listed on a map published only 10 years ago would be off by 3 degrees or more. I always go to http://www.ngdc.noaa.gov/geomag-web/ to check current declination for an area.

Useful methods: I haven't found resection (or "triangulation") to be that useful for land navigation, though it is useful when boating. If I have several clearly identifiable landmarks around, I can usually figure out pretty closely where I am. However, I have sometimes found a variation on this method useful. If one is on a linear feature such as a ridge line, and has a single well identified landmark in view, one can plot an azimuth from the landmark to the linear feature and get a good fix. Deliberate offset (aka "angle off" or "aiming off") is also handy. The requirement here is that the objective be located along an easily identifiable linear feature.

Best type compass: For me, I find a good mirror sighting compass, with adjustable declination and a clinometer is the most useful. For getting a general direction I can use it like a baseplate compass. For more precise work I can use the sighting mirror. The clinometer is essential for getting accurate slope angles when traveling in avalanche terrain (those who don't go into avalanche country probably don't need it).

When I've needed a compass the Suunto MC-2G was more than adequate.


Lately all I use is a Suunto wrist compass which is lightweight and very convenient. I have a GPS (or two) just in case, but they're usually turned off.

"Just in case" is why we practice navigation with all the tools at our disposal rather than just using GPS all the time. Map & compass, map without compass -- GPS should be a training back-up, not a primary navigation tool. What's the fun in knowing where you are within a couple feet without doing anything but turning on an electronic device; try doing your navigation without the "tech".

Re the Pocket Transit... Maybe Orienteering with a compass that was a bit more accurate such as the Brunton Pocket Transit could be compelling. Does anyone geo-cache without a GPS?

Yep, the Suunto MC-2G is my current 1st choice as well. It has an "international needle" just in case I ever make it to Patagonia. I also sometimes use the Suunto M9 wrist compass, so I guess great minds think alike!

I've never even heard of the fluid inside a compass thickening or freezing, but I tend to avoid such super-cold conditions. I'd think keeping it close to the body and warm, like on a neck lanyard, should prevent that.

Having dealt with compass bubbles before, I've wondered why capsules are sealed instead of having maybe a thick, flexible and removable plug to deal with that.

I also have a tiny little brass compass as part of my EDC.

I once ordered a K&R compass years ago, but was unimpressed with it.

The Magnetic North Pole does move around, but I suspect it has a much larger impact in Alaska and Canada than in the lower 48. NOAA offers a website that provides current magnetic declination for any location, if you want to update old maps. [edit: as ASKAR already pointed out]
http://www.ngdc.noaa.gov/geomag-web/#declination

Army issue gear does not imply it's free of flaws. Take any prismatic disk based liquid filled compass and try tilting it a little in various direction, while looking through the eyepiece. You'll see what I mean. Also observe the speed your disk/needle goes back horizontally. It is slow enough to be a bad bubble level substitute, especially if you are in a hurry to make a quick fix at your walking direction.


My hiking stick/monopod is aluminum alloy, including the screw, and I see the utility in using it when necessary as I do have professional surveyor training and work experience (even though quite dated and with military roots; by the way, my military battlefield surveying tools were far less advanced compared to that $5 eBay compass, but still all of my rather small training targets were always hit from the second burst). Also, for those liking the mirror to measure azimuth of peaks and tall trees, what do you think will happen to your data, if your compass is not level when measuring at the top of the slit?


That's a bad method, as I can see at least 4 opportunities, where an error can be introduced (and not compensated by each other). Also "more or less exactly" is not an acceptable criteria for compass calibration either

So, I'm still not convinced that I must have a brand named $100 ancient mechanics plastic compass with the view obscuring mirror, instead of the $5 "prismatic", where the unreliable expensive prism on a hinge is replaced with the retracting direct view eyepiece (which is a huge improvement of the measurement technology having direct impact on reliability and precision).

Get a free planetarium app for your smartphone. Given it has a recent GPS fix (or you can tell and input your location coordinates within a 100 miles error spot) you can figure the magnetic declination measuring the azimuth of any visible celestial body with your compass (e.g. Sun, Moon, any bright star poking through the clouds). All of them are capable of showing the true azimuth of any celestial body in real time, just subtract the two.

Hmmm, the accuracy of those Planetarium apps is dependent on knowing where you are to synthesize the night sky. Further, the same cellphone that has the app also has a fairly accurate electronic compass. What's is our objective?

I'm Android developer having the best on the planet handheld Star Chart app in my portfolio (DSO Planner - it's not exactly the planetarium app, more like a professional tool, but still having similar capabilities). You can trust me on that:

1. The smart phone compass (and the inclinometer as well) is just slightly more precise compared to a primitive button compass. Moreover, its data is unstable (put it on the table note the azimuth and orientation, grab it, put back into the exact same orientation - most likely you will see a different azimuth value). Any real compass would work much better (and not consume the battery).

2. If you have a knowledge of your location with even a 100 miles error, your planetarium software will have an error in objects positions of just 1-2 degrees max (the Moon may have an additional 1 deg. error in a worst case due to the parallax effect), which is comparable or below the accuracy of your ordinary compass measurements. Besides, you have a topo map at hands to orient, right? (they usually have the coordinates grid or center's coordinates imprinted)

Even though you have a GPS on your phone, it wouldn't tell you the direction, unless you are moving fast enough or/and record and periodically monitor your trail path on the digital map. Don't be fooled with the car navigation apps, they are approximating your position and direction using the map data (aligning the GPS data with the road lines exactly).

??? This is way too complex! Polaris, the North Star is no more than one degree from true north. Find Polaris and you are looking north. End of problem. This has been common knowledge before smart phones, much less the apps you could load on them... Other stars are fixed in place, and with a reasonable amount of observation, serve equally well.