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The Compass - Know Your Choices
A compass is the basic tool of navigation. They come in all shapes and sizes and there are many types to choose from. So let's take a look at the various configurations so you can better select the one that is best for you. I would recommend that the one you choose be a liquid filled compass, which slows the swinging of the needle, called damping, and makes the needle stop faster.
A button compass is a small compass capsule with no frills. Some are liquid filled and some are not. I recommend only those that are liquid filled. It is a Floating Dial compass, but not free floating. It does have a pivot point on which the dial sets, which allows the dial to rotate, but keeps the dial away from the sides of the capsule. This is why it is important to hold the compass level in order to get an accurate reading. Size often dictates features, and with a button compass, there are no features other than the ability to determine direction. For reason, I would never recommend a button compass as your primary compass, only as a back-up. However, because of its small size it is a good compass for a mini survival kit.
Button compasses can often be found as part of various items that can be used a zipper pulls. They can include a thermometer, a wind chill chart, or a mini base-plate. Again, I only recommend them as a basic means in which to determine direction.
This photo, from left to right shows a 14mm button compass over a 20mm compass, a 14mm compass zipper
pull with thermometer, a zipper pull 20mm compass, and a 20mm compass with mini base-plate.
Button compasses are available in various sizes, with the most popular being the 20mm and 14mm. Unless size is a real issue, I would recommend the larger 20mm, as it is obviously easier to view than the smaller 14mm. Both are offered in Grade-AA and A. Basically, the difference between Grade-AA and Grade-A is the AA should have no bubble of any size when constantly observed at 70°F. A Grade-A is allowed a bubble less than .075" when constantly observed at 70°F. I prefer the Grade-AA, and although only slightly more expensive, in my opinion are the best.
I have found it handy to have a compass on the wristband of my watch, as a backup for quick orientation. Although not my main compass, it is always available, just in case.
A nice wristwatch band compass is made by Suunto and is called the Clipper™. The Clipper™ is a Floating Dial compass and has a nice mounting system that allows it to be clipped on a watch band, to clothes, equipment straps, etc. (or even clipped inside a survival kit). It is liquid filled with a jeweled bearing and has directional points and a rotating/ratcheting dial. It even includes a wrist strap. I had had one on my watchband for at least ten years, and my wife still does.
Wrist compasses, from left to right, are the Suunto Clipper, Suunto M-9, and the Cammenga.
This shows a Suunto Clipper compass on a watch band.
Another wrist compass, which I now wear, is the M-9 Wrist Compass made by Suunto, which is a compact, highly accurate wrist compass. The unbreakable black polymer housing has a sighting window for accurate bearings, and sighting points on top. You do not read this compass from the top, as the bearing markings are reversed on top. You read it through the side, so that when "O" degrees appears in the side window, you are travelling north. The easy to read face has luminous markings for night use. A 2.5 degree ratchet mechanism can be used to set desired a direction. A Hook & Loop wrist strap is included.
This shows the sighting system through the side of the Suunto M-9 wrist compass.
Another wrist compass is made by Cammenga and they offer both a Phosphorescent and Tritium model. They are light weight with a machined aluminum casing. These compasses have a Sapphire jewel bearing with induction damping and include a heavy duty nylon wristband. They are only considered "water resistant" and I have had problems with condensation in them in rain. I called the manufacturer and they told me I would just have to wait until they dried out. I stopped using them.
Fixed Dial Compass
Often looking like a pocket watch with a pop-up cover, these were often carried and used by outdoorsman, mainly because they were inexpensive. However, they not very accurate and they usually do not have a damped needle in order to slow the needle travel.
This photo shows a couple fixed dial compasses from my collection.
These compasses have a fixed dial and usually only show the major compass points. Rarely do they provide a sighting device or an arrow for direction-of-travel, making them only suitable for showing general direction. Basically, they are nice to look at, but would not be my recommendation for real orienteering or wilderness use.
For general orienteering and for use with a map I prefer a Base-Plate compass, also known as an Orienteering compass). These have a transparent plastic base with a compass capsule that is independent from the base. These type of compasses are designed to be used with a map and make traveling in a specific direction much easier than with a fixed-dial compass. Base-Plate compasses are available in basic to advanced models (larger size so more frills). They range from basic orienteering to options such as sighting mirrors, adjustable declination and clinometers. Of course, if you don’t have training with a compass I recommend that you get some before a survival situation occurs!
When choosing a Base-Plate compass, I suggest you stick to the major manufactures. Some of my favorites are Suunto, Brunton (which is now owned by Silva), and Nexus (which is the brand name for Silva compasses sold in the U.S.) . There are some cheaper compasses out there, but a compass is not something you want broken, or inaccurate, when you go to use it. You must be able to depend on it.
This shows an example of Base-Plate compasses.
I recommend a luminous dial, when available, which is handy for using in the dark or low light conditions (Tip: If a luminous dial does not glow, shine a flashlight on it for a few moments and it should glow for several hours.). If you plan to use an orienteering compass in conjunction with a topographical map, and you do not adjust your maps for declination, you should get a magnetic declination adjustment feature. Although not necessary, as you can always add or subtract the deviation at each reading, the stress of a survival situation could cause you to forget to make the mental calculation. If you are not familiar with declination, this may not sound important. However, if you were in the eastern or western most parts of the U.S., the magnetic declination can be as high as 22 degrees. If you didn’t take this into consideration, you could be more than a mile off your destination at a distance of 3 miles.
This photo describes the various parts of the Base-Plate compass.
Many orienteering compasses also have a small magnifying glass in the clear plastic base. Not only can it be used to magnify the finer features of a topographical map, but it falls into the category I call “multi-purpose use”. It can also be used to see a splinter for removal, or even for fire starting. This goes the same for the mirror on a mirror compass, which will be discussed next. It could always be used as an improvised signal mirror, or to check those difficult areas for ticks.
Some Base-Plate compasses also have a sighting mirror. This provides you with a more accurate means in which to sight your compass when navigating. I have come to prefer a mirror compass as my main compass, and carry one on each pack. These compasses are basically a Base-plate compass that has a hinged mirror attached at the top.
This shows some Mirror Compasses from my collection. The one on the right is the Suunto MC-2 which is one
that I use regularly in the field for navigation.
In order to explain how they are more accurate, a quick lesson in compass usage. With a normal Base-plate compass, you hold the compass in front of you, about mid-chest level. In this manner, after setting your bearing, you can see that the magnetic needle is in the orienting arrow (I call this boxing the needle). You must now raise the compass in order to sight on something ahead. However, once the compass is raised, you can no longer tell if "The needle is boxed". Therefore, it is common to see users raise and lower the compass several times to ensure "the needle is boxed" while trying to aim ahead. The problem is that it is impossible to see if "the needle is boxed" while the compass is raised, and is very difficult to accurately aim the compass when it is lowered.
The mirrored compass solves this dilemma and allows very good accuracy while aiming. This is how a mirrored compass works, and why it is more accurate than a regular base-plate compass. You can hold a mirrored compass up at eye level, and adjust the hinged cover with mirror at an angle which allows you to see the orienting arrow and the magnetic needle. On some mirrored compasses, there is a line down the middle of the mirror. This line should run through the center of the center pivot point of the magnetic needle. This will ensure that you, your compass, and the object your aiming at, is in a perfect straight line (which limits lateral drift).
A Mirror compass can be held up at eye level, and still see the the needle through the mirror, which provides accuracy.
This shows the arms straight out sighting straight through the compass.
If you want to determine an azimuth, hold the compass at eye level, and using the aiming sights, place them on a distant object, such as a tree, etc. You then rotate the graduated azimuth ring until the north end of magnetic needle (normally red) is within the north side of the orienting arrow (normally red, but as in the picture above, it can be green). Without having to bring the compass down to chest level to turn the graduated azimuth ring, and with the optimized "V" sighting points, your accuracy has just improved over the technique for a base-plate compass, whereby you must constantly raise and lower the compass to determine if the magnetic needle is in the orienting arrow. Now, if you already have an azimuth dialed in the compass, you simply raise the compass to eye level, and while viewing the magnetic needle in the mirror, turn your body until the needle is in the correct position in the orienting arrow. You can now aim on something that is straight ahead in the sites, and you know you are traveling on the desired azimuth. Again, you don't have to raise or lower the compass. As you can see, a mirrored compass provides for increased accuracy.
This shows the sighting through a Mirror compass with the needle visible in the mirror.
The best two mirrored compasses I am aware of are the Suunto MC-2DL and 2DL Global, and the Silva Ranger 515 CL & CLG. These are very respected mirrored compasses and provide for very accurate navigation. I prefer the Suunto model and use the standard MC-2DL, as well as the MC-2DL Global, which has a global needle system, so it works anywhere in the world. An additional sighting hole makes for superior accuracy and the luminous two-color bezel ring is very easy to see and use. A jeweled bearing, clinometer, large mirror with center line, clear base-plate with magnifying lens, and a detachable snap lock lanyard round out this great compass. It measures 2.5" x 3.9" x .6", and weighs 2.65 oz. This is the compass I carry and use for outdoor adventures.
The Lensatic compass is a Floating-dial compass that is used primarily by the military. The floating dial is mounted on a pivot point so that it can rotate freely when the compass is held level. An arrow and the letters "E" and "W" are printed in luminous figures. There are also two scales on the disc, the outer scale for mils and the inner scale (normally in red) for degrees. The floating dial is encased in glass which has a black index line. The bezel ring is a ratchet device that clicks when turned. Each click is equal to 3° with a total of 120 clicks when fully rotated 360°. It has both forward and rear sights for aiming. It also has a hinged lens, which contains the rear sighting slot, that is used to magnify the scales on the floating dial. It also has a finger loop for holding the compass in the raised position.
This shows a Cammenga Lensatic compass in hand.
There is much debate on the accuracy of this type compass. Some say it is very accurate, while others indicate it is only theoretically more accurate. I will stay out of the debate and indicate that you should use what you are comfortable with, or what works for you. I do feel, that compared with base-plate compasses, this type of compass is not as versatile nor is it as easily used with a map, at least in my opinion. I carried one in the U.S. Marine Corps., and when I left, I left this type of compass behind.
If you do select a Lensatic compass, get a good one. The best is made by Cammenga®, who is the exclusive manufacturer of the official U.S. Military Lensatic Compass. It is built to the demanding specification of MIL-PRF-10436N, and is battle tested against shock, water, and for being sand proof. It is functional from -50ºF to +150ºF. It also has seven Tritium Micro Lights which allow for navigation in low-light conditions. It is equipped with a magnifying lens, sight wire, and dial graduations in both degrees and mils to ensure accurate readings. A copper induction damping system slows the rotation of the magnet without the use of liquids. This compass is built to last with an aluminum frame and a waterproof housing.
Originally, I had not included the Pocket Transit in this article, however, I had a reader comment that I left it out of the article. Actually I did, because my articles are generally about wilderness survival and navigation to that end. In over 40 years of navigation and orienteering, I have never run into anyone who used a Pocket Transit for general navigation, although that doesn't mean nobody does. However, for those who are interested, here is a general description of the Pocket Transit Compass.
A Pocket Transit, also called a surveying compass, is a precision compass, considered a specialized instrument, used by those needing to make accurate degree, and angle measurements in the field such a geologists, archaeologists, environmental engineers, surveyors, and timber cruisers. The U.S. Army also uses a Pocket Transit for use by crew served artillery.
The Pocket Transit is an expensive precision instrument not normally used for general navigation. On the
left is A Brunton Convetional Pocket Transit Compass, price $399.99, and on the right a Brunton GEO
Pocket Transit Compass, price $599.99. Photos by Brunton.
The Pocket Transit is usually made from solid aluminum and waterproof. As opposed to a fluid damp needle, it uses a magnetic induction damping. It has a needle locking mechanism that locks the needle when not in use. It has a precision aligned mirror with see-through sighting capability. It can be adjusted for magnetic Declination. There are many other features but you can see that this is a highly specialized instrument. It is also expensive, usually ranging between four hundred and six hundred dollars. Because of the expense and intricacies of a Pocket Transit, it would not be my recommendation for general navigation or use with a map.
As you can see there are many choices when it comes to a compass. For real navigation, I highly recommend that you get a good grade Base-Plate Compass (a Mirrored Base-Plate if you can afford it) or Lensatic compass, depending on your preference. I would probably avoid Fixed Dial compasses except for general direction. Both Button and Wrist compasses should be considered back-up compasses and not relied on for accurate navigational purposes.
I hope this article has helped you better understand the types of compasses available. I highly suggest that you get some real training in the use of a compass as well as a map.
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Copyright © 2016 by John D. McCann