C'mon, that's just subtracting two numbers I'd like to see you finding Polaris at noon (if you are not at the North Pole in winter). Or when you are in the South America...

At noon, I would be using the big fusion reactor in the sky, which I would have been observing carefully since dawn. If I am ever south of the equator, it will be back to the drawing board. I understand there is something known as the Southern Cross....(but it only point south???) Better I should stay up north.....

There are plenty of ordinary situations when you cannot rely on just a single star, thus a compass was invented. The Southern Cross is more like a Southern Big Dipper. Just easy to identify (even though I had a trouble doing that at the first time long ago, as somehow expected a star in its center ), but it is quite far from the true South point for any compass calibration. My point is that a planetarium app on the phone can help you with any celestial navigation tasks from just objects identification to a serious sextant work.

I would think a compass was invented and developed for the proverbial dark and stormy night, especially when at sea. When i have been at the helm at night, I have used both stars and compass - pick a star that is on your bearing, and then steer by that. Just recalibrate every now and then.

I know that trick from my father, we sailed the Japan see a lot that way, really rural west shores, ancient motor boat. Wrist compass, no GPS, no radar, nothing. Just amazing starry sky above and the same stars below (glowing plankton). That's probably exactly what has triggered my deep interest to the astronomy.

Alex, maybe it's a matter of semantics to some degree, or a different approach to working with a map and compass in general but I'm not really sure I understand some of the points you've made in your recent posts.



I brought up the M73 Francis Barker because it's a darn good prismatic compass, and quite typical for its class. It's a mil-spec design but that is totally beyond the point. This is the kind of compass used for precision work in the field, with an excellent track record. Compasses of virtually identical construction have been used by soldiers, explorers and adventurers from Livingston to T.E. Lawrence, so I guess it says something about the longevity of the design.

Not sure where you got that "unreliable expensive prism on a hinge" - the M73 (and pretty much all comparable products) is built like a good old Swiss watch, plus it's plenty sturdy enough for serious field use. Those $5 eBay wonder compasses are not, IME.

The M73 - or any other similar prismatic compass - is capable of very precise measurements as long as the user is vaguely competent in its use. Among other things, this involves holding the compass in a reasonably stable and level position, which I suppose is straight-forward and self-explanatory enough.

I'm not exactly sure what you mean by your previous training or "battlefield surveying tools", but a precision compass is about the most basic tool used for field surveying, and also quite popular in some branches of the armed forces. The Brunton Pocket Transit, the US M2 artillery compass and the British M73 are good examples of their type.

I'd think that anyone trained in land surveying methods of any kind would be well familiar with that sort of equipment and the accuracy it can achieve. BTW, I have never, ever seen any professional mount a compass on a monopod (or a walking stick for that matter). The idea is beyond me, and I can't fathom what one could gain that way. A tripod-mounted surveying compass is a different matter - but now we're getting into a whole new ball game, which really has nothing to do with general land navigation.

Either way, any decent prismatic, lensatic, mirror... even baseplate compass can achieve an accuracy far better than what you stated...



In skilled hands, a modern baseplate compass can get within +/- 3 degrees (limited generally by the lack of sighting aids rather than any other inherent weakness).

The eBay compass that you seem to hold in high regard falls into a different category, however. If it works well enough to suit your needs, that is fine. But being familiar with that particular product, I would not recommend it to anyone.

I'm not saying everyone needs a "$100 ancient mechanics plastic compass" (??) with the "view obscuring" (uh-oh???) mirror.

I do believe however that anyone serious about outdoor pursuits of any kind should learn at least the basics of map & compass use. Once you master those fundamental skills picking a good compass - one suitable for your specific needs - will be an easy job. Either way, my suggestion would be to look for a quality compass you can rely on instead of wasting your money on inferior no-name products. Land navigation is a pretty serious skill, so there's really no place for worthless gizmos and inferior no-name products.

As always, YMMV

Tom, would that help if I'll explain that I've been serving in the Soviet army? Where most of the problems are resolved with a sledge hammer or with just a strong taboo word magic...

Let me explain the obvious to me "prismatic" M73 compass (P) flaws vs (N) $5 noname compass advantages as well:

1. P uses a prism on a hinge, N does not have any prism nor a hinge there (so the N is mechanically more reliable and less expensive to manufacture).

2. P's prism obscures the dial when engaged, N's dial is always open.

3. P has a fixed lens after the prism, N has an adjustable lens (great if your vision is not 20/20)

4. P has an eye sight slit on the prism's body. If you bend or damage the hinge you will have a wrong sighting if any at all if it lost (the prism's internal hairline will be shifted as well). N has that sight fixed on the monolithic compass body.

5. The P's prism mechanism has no hard stop in the engaged position (over the dial's glass), it is possible to have it engaged only half (or even if 7/8) way and have the measurements done without even noticing that. But in case of just slight misalignment of the hinge you will have a systematic error introduced. Yes, they are tested at the factory, but only in the 100% engaged position.

6. The dial of the P has their most precise ring numbers mirrored (prism is mirroring that image back to normal) - that makes it less readable for a direct view (asking for silly human error). N has totally normal numbers.

7. When you disengage the prism on P it's protruding far from the body making it vulnerable to various forces. N lens is screwing almost flat into the body.

8. P eyepiece lens is mounted almost on the surface (maybe 2mm deep maximum, and beveled out, why?), N lens is deep (about 5 mm) in the holding black tube (what makes it almost entirely glare free and protected from any abrasion chance).

9. P dial's degrees lines are obviously radial, N's are much closer to parallel being on the vertical slope (what makes it more reliable when taking measurements for fractions of a degree).

10. P's dial as visible from the eyepiece has no information about the levelness of the compass, N's side view reveals even slightest slope in any direction immediately.

11. When used in direct view mode, P has no bubble level and it is very hard to see if the disk is level or not from the top (easier with the needle - true). N has a dedicated bubble level on the top.

12. P and N have exactly the same front sight, which is a transparent window versus typical non- or semi-transparent mirror with a slit in non prismatic alpine compasses (that's the answer to your question about the mirror).

13. P has round body, N - square (what is better for map work?)

14. The tripod mount is great to have than not to have it at all. Perhaps, you could understand its utility better if you can imagine replacing the "tripod" word with the "sturdy and level table" words? Have you ever tried to map a terrain on piece of paper with an ordinary compass? I did, and I did the same with a theodolite on tripod as well.

15. There could be more.

Regarding the typical baseplate compass measurements precision. I meant the compound accuracy (mechanics, techniques, conditions). I said it is 10 degrees. You are insisting on +/- 3 degrees, but that's 6 degrees overall. Add dial/needle/sight view parallax errors, add lack of levelness, add impatience for needle setting - and you can round it up to 10 without a single doubt (I'm leaving magnetic anomalies and lack of mag.dec. precise knowledge outside of the scope). And that's exactly the ancient compass technology flaws, you have mentioned yourself, as the primary source of these errors.

Also I don't like the "skilled hands" notion. I understand the pun and paraphrase behind, but perhaps you don't? The skills here are is the deep knowledge of your tools and of the proper ways to overcome, amend, correct your data for any flaws they have and which might influence specific measurements. No mill.spec or the price guarantee you don't have any (see the list above). And I have stated at the very beginning that in the skilled hands all that matters in a classic compass is the concentricity of the dial with the needle pivot. The rest are just skills. However, the compass I've presented above is the improvement over the classic (ancient) model (the M73 is too, but the N is way better, because it's not struggling to be a Swiss Watch, but rather a very well thought out pocket compass). You can find the exact same scheme and features, which you can get for $5, in multiple models of $800 survey compasses. But there is no a single reason you have to pay 160 fold more to have all of that tech advancements, eliminating or minimizing many classic model flaws, for an ordinary field navigation.

The longevity of the design? Millions of happy users? The digging stick is much more reputable than a shovel then.

Alex, I'm afraid I have to politely disagree with you. It is entirely possible for a careful user to get within +/- 2 degrees using a mirror compass. This includes ALL of the compound errors. I have participated in compass training exercises which required walking a course and finding small, obscure targets. If you were more than 2 degrees off over a distance of 100 to 200 meters, you would walk on by and not find the correct target.

This kind of accuracy does require careful work, but it is doable.

I don't know what compass you were using, but maybe you simply had a too refined training setup? For example, the teacher could first measure the apparent Azimuth of the target from the start location with that exact compass and give you that number along with that very compass, even though the true azimuth of the target was off by 5 degrees, e.g. because of the compass dial excentricity. (by the way, the mirror already does not belong to the classic model we discussing, as it eliminates several obvious issues to some degree). Even a 0.1 deg. accuracy is achievable on a level table (with big enough dial), especially if you care to account for your particular compass pivot drag. But when you are on a trail and taking bearings every so often on the go, you will see my numbers or even worse ones. And the price of the compass wouldn't help to improve that if it is of a classic type with less than 2" needle. I believe that being conservative on your compass capabilities is better than rely on its ideal test conditions technical specs blindly.

Alex - dunno, I've played a fair bit with ex-Warsaw Pact compasses and on the whole, they tend to work about as well as comparable Western products. It's just that the overall package tends to be a little less refined and with fewer bells and whistles occasionally.

We could probably argue this back and forth, but I'll just add a few more points to consider.

1) The eBay special under discussion is basically a rip-off of the old German "Wilkie" compass (a similar, but not identical version is produced nowadays by K&R as Meridian Pro). The "Wilkie" was an excellent compass in its day, whereas the eBay version is made to far lower standards. BTW, the Meridian Pro has been "copied" as well by the same manufacturer, with equally unimpressive results:
http://www.ebay.com/itm/New-Professional...sid=p5731.m3795

2) Any type of compass can be damaged. Mirror, lensatic, prismatic, doesn't matter. What makes you think the eBay compass is less susceptible to damage than say, an M73?? A few examples of the same eBay model that I've tested myself have been very poorly made and on several I couldn't even open the cover properly because the hinge was bent so badly that it needed some manual "straightening" first.

BTW, I can't really imagine bending the prism hinge on an M73. I'm sure it could be done, but it would probably take a hammer and a lot more abuse than any compass could be expected to take.

3) What good does that spirit level do on a compass used for practical land navigation (as opposed to geology, surveying and such)? How do you focus on the compass needle AND the spirit level simultaneously? Myself, I find it a little easier to focus on the compass needle alone and at the same time it gives me a pretty solid indication if I'm holding my compass level.

4) As far as the M73, have you actually had an opportunity to use one in the field? I haven't been able to identify any real problems with its design or manufacturing quality and I certainly can't relate to your list of supposed construction "flaws". It's true that the M73 is not ideal for working with a map, I will give you that - but you still have the sighting line on the lid that gives you an accurate straight edge to work with.

BTW, the "Wilkie" ripoff does not exactly shine at map work either. A simple baseplate, or a mirror baseplate compass, would be more convenient for that purpose. A separate protractor would be even better.

Anyway, you have to ask yourself what you're actually trying to achieve with a compass. Basic land navigation? Orienteering? Drawing maps? Surveying? Horses for courses, each task calls for a specific type of equipment.

At the end of the day though, you get what you pay for. So...



Well, sadly - no, not in my experience at least. I haven't ever used a $800 compass, but I would always consider the good old M73 and the Brunton Pocket Transit (each about half that figure) a good investment if you're into that sort of thing.

For most people though, something from a $20 baseplate to a $50 mirror compass or the Cammenga lensatic would provide all the performance generally required in the field, in a reasonably reliable, easy-to-use package.

As for the $5 eBay wonders... Don't see them used much for any serious purpose, for a good reason I suppose.

And for all the stiff market competition these days and the Chinese churning out el cheapo compasses by the truckload... The good old Suunto, Silva, Brunton, Cammenga etc. are still in business. Maybe they're doing something right?

YMMV - over and out.