Maps/Navigation #3, 6/13/99: Orientation, Part 3, Using Magnetic Compasses

	Adjustable Compasses (Maps/Navigation #3, August 7, 1999) Adjustable compasses have a compass body with a lubber's line and a rotating capsule or bezel with a boxing mark. They do the same things as the simple compass, but they are more versatile. The simple compass is designed to use by turning the entire compass relative to the earth. The adjustable compass allows you to turn only the capsule or bezel while keeping the compass body always pointing forward. This makes the adjustable compass easier to hold and easier to align while walking. To Determine a Magnetic Bearing with an Adjustable Compass
	(1) Stand directly facing the landmark. (2) Hold your compass directly in front of your body. (3) Look down at the compass and point the lubber's line toward the landmark. For Needle Compasses: (4) Hold the compass body steady and box the needle by turning the capsule. ...then The lubber's line indicates the landmark's magnetic bearing on the azimuth circle or compass card. To Walk A course with An Adjustable Compass
	(1) Hold your compass directly in front of your body. (2) Look down at the compass and point the lubber's line directly forward. For Needle Compasses: (3) Hold the compass body steady and turn the capsule until the lubber's line points to the desired course on the azimuth circle. (4) Turn your whole body to box the needle. For Card Compasses: (3) Turn your whole body to align the lubber's line with the desired course on the card. ...then The lubber's line points directly toward your course. Look up and find a landmark directly in front of you as far away as possible. Walk toward the landmark without referring to your compass. When you arrive at the landmark, repeat this process for a new landmark. Sighting Compasses In sighting compasses the lubber's line is augmented by a front and rear sight, or some other pointing device, which allows very fine landmark selection—you can easily sight on the trunk of a tree or bush. Actual bearing resolution is still limited by the resolution of the azimuth circle—typically about 2º. There are two types in general use:
lensatic compass	The lensatic sighting compass is almost always a card-type compass with front and rear peep sights. Lensatic sighting compasses are so simple and rugged and incredibly easy to use that it is no wonder they are the standard type used for orientation by the U. S. Army and Marine Corps. They are very widely available from less than ten dollars to more than seventy (except for pride of ownership I've never seen the need for more than the lower-cost models.) You can expect accuracy to within a degree or so. Mirror sighting compasses are usually needle-type compasses. They have found favor with European armies, and like much European military equipment, they are somewhat overdesigned and underbuilt. They are not particularly simple or rugged or easy to use; and they aren't as cheap (about $20 to $75) or as easy to find as lensatic models. But they are accurate—to within a degree or so.	mirror compass
	Whichever type you use, remember that lots of field practice is the key to using any compass accurately, confidently, quickly. This is especially true of sighting compasses, specifically mirror sighting compasses. Sighting compasses used without their sights are no more than the simple or adjustable compasses we've discussed. In the three basic orientation operations, taking a bearing, walking a course, and plotting a fix, you can use them the same way. It's in making precision landmark selections that these compasses shine, so I'll cover only the basic use of the sighting feature for each of the two types. How to Use A Lensatic Sighting Compass To take a bearing
	(1) Open the compass cover/sight and adjust the rear sight so you can look up and use the sights and look down and see the card azimuth circle through the magnifier; (2) Select a landmark and sight on it with the front and rear peep sights; (3) Look down through the lens at the card; the lubber's line indicates the bearing. To walk a course (1) Look down through the lens at the card; (2) Hold the compass steady and turn your whole body to align the course on the card azimuth circle with the lubber's line. Box the card with the bezel index as a reference. (3) Look up through the peep sights and select a prominent landmark as far away as possible; (4) Walk to the landmark without regard to the compass; (5) When you arrive at the landmark, repeat the process for the next leg of the course. How to Use A Mirror Sighting Compass To take a bearing
	(1) Open the compass cover/mirror and position it at an angle of about 45º; (2) Align the landmark with the sight(s). Keep the mirror sight line aligned with the lubber's line; (3) While looking in the mirror, turn the azimuth circle to box the needle; (4) The lubber's line indicates, on the azimuth circle, the landmark bearing. To walk a course (1) Open the compass cover/mirror; rotate the azimuth circle to align the course with the lubber's line; (2) Hold the compass steady and turn your whole body to box the compass needle; (3) Position the compass cover/mirror at an angle of about 45º; (4) Sight through the sight(s); keep the mirror sight line aligned with the lubber's line; (5) Select a prominent landmark; (6) Walk to the landmark without regard to the compass; (7) When you arrive at the landmark, repeat the process for the next leg of the course. During my practice with the two sighting compasses I got very good results; taking accurate bearings was no problem. But I've not yet really gained confidence with the mirror compass; there are just too many things to keep in my mind at once. My only criticism of the lensatic compass is the inclusion on its card of the "mil" scale, an engineering and surveying scale that is used on military compasses to align artillery. Since I don't do that very often, the mil scale is useless to me. It degrades the elegant simplicity of the lensatic sighting compass. Why is it still there? Two possibilities: (1) to make it seem more "official" to military wannabees; (2) because our Asian friends, who are so good at copying items and producing cheap knock-offs, don't understand or care what the users of their cheap copies really need. So the stupid mil scale remains, cluttering the outer rim of the card, prime azimuth circle real estate for achieving high bearing resolution.

	What Kind of Compass Should I use?
Lensatic sighting compass	While I prepared this article I used several kinds of compass. I liked them all, and I'm glad I bought them. Three stand out as easy to use, practical, and rugged: (1)The simple needle compass. It's not fancy or complex; it's just right. I used the inexpensive Nexus (Silva) "Sidekick," and I liked it so well I've stocked it in the Spider Cañon Store. It's compact, inexpensive, accurate; and it has a large needle and azimuth circle. (2)The lensatic sighting compass was great for taking tight bearings and fixes. With its card-type design, it was generally very easy to use. This compass is available in discount stores and hardwares almost everywhere—very inexpensively.	Spider Cañon Sidekick
	(3)The orienteering compass—an adjustable needle-type with a declination scale. The cheapest I found is the Silva "Polaris"; from outdoor stores—about $10. Truthfully, I used it most often as a simple compass, which made it really only a little better than my Spider Cañon "Sidekick." The best thing I learned in all this is that any compass that works is useful, and that having several is a safe way to work. In this article I've concentrated on using compasses, outdoors, for direct basic navigation applications. Using compasses and maps together there are many other applications, both direct and indirect. I'll cover them in the future. Now...	Silva's "Polaris" orienteering compass

It's Fun Time

Up to now it's been words, words, words, and a few pictures. How about some real practice?

Get a compass, any kind. I recommend an inexpensive adjustable needle compass like the Silva "Starter" or "Polaris." They're sold at better outdoors stores everywhere. A good internet source is www.campmor.com. You can also use the Spider Cañon "Sidekick," a high quality, low cost, liquid-filled simple needle compass. See our Store to order.
Find a location near you where you can practice taking bearings and walking courses. A local schoolground or park is ideal, just so you are not near any masses of metal.
Practice taking bearings and walking courses using your simple compass or using your adjustable compass as a simple compass. Use the "working to a number" and "working to a point" methods; and practice marking your locations visibly.
Practice taking bearings and walking courses with your compass as an adjustable compass.

For many more interesting orienteering exercises see Be Expert with Map and Compass, by Björn Kjellström. It's available from our Online Bookstore

While preparing this article I quickly discovered that no one reference had all the right information. I had to do a lot of editing and sorting. I've tried to express these basics clearly, as simply as I can. Here are some of the books I found useful:

Be Expert with Map and Compass

Björn Kjellström Be Expert...

GPS Made Easy

Lawrence Letham

Be Expert with Map and Compass, Björn Kjellström. Kjellström is a recognized pioneer in orienteering, and one of the inventors of the adjustable compass. His book contains many map and compass training scenarios suitable for orienteers of all ages.

Mountaineering The Freedom of the Hills, The Mountaineers. An excellent reference in all aspects of working and living in the outdoors; excellent section on map and compass.

GPS Made Easy, Lawrence Letham. Mainly about GPS, but contains an excellent scenario on what to do when GPS fails.

Land Navigation Handbook, W. S. Kals (Sierra Club). Kals seems more interested in being clever than useful, but there are some interesting subjects covered.

You can order these four books via our Online Bookstore.

Mountaineering: The Freedom of the Hills

The Mountaineers

Land Navigation

Land Navigation Handbook

W. S. Kals

Map Reading and Land Navigation

U. S. Army

Army FM 21-26, Map Reading and Land Navigation. The updated version of this field manual is actually available online: FM 3-25-26.

"Silva Compass Information," The Silva Co. This is the simple, excellent brochure that accompanies each Silva compass.

For Internet tutorials on map and compass see the Navigation Education Links in our Reference Library. If you find other good books or links, or have any comments about this article email me at:

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See you next time for:

Orientation, Part 4—Using Compasses with Maps.

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