Monday, January 27, 2014

Buying a compass

Your compass is one of your most important pieces of gear for orienteering or adventu
re racing. Having a compass that is functional and easy to use is important. If your compass doesn't have these qualities you will use it less often during the race...and you will be lost more often.

Compasses come in many shapes, sizes and costs. There are some very good cheap compasses and there are not-so-great expensive ones.

My favorite compass has been the Suunto M-3DL. I had one of these for several years until I lost it on the way to a race 2 years ago. It was a sad day. The replacement compass I bought, in desperation on the way to the race, was the Brunton Classic. There's nothing like a bad compass to demonstrate how important it is to have a good one!

Features to look for in a compass

When buying a compass for racing there are some attributes that you will want high on your priority list:
Suunto M-3DL - Good value compass
  • Long base plate - A longer base plate is a feature that I like in a compass because it allows you to line up features further apart on the map accurately when taking a bearing off of the map. If you have a too short base plate you will end up either estimating the extended straight line on the map or carry another straight edge with you to extend the line.
  • Dampening fluid - The dampening fluid in a compass keeps the needle from jiggling around while you move. You want a compass with dampening, but not excessive amounts that make the compass slow to respond when turning. Try out the compass, walk around with it, turn and twist it ,and make sure that the needle responds in a way that is comfortable for you to follow. 
  • Adjustable declination - Many cheaper compasses and some more expensive ones don't provide declination setting. As previously discussed, accounting for declination is important! Some will provide a declination reference on the face, this isn't sufficient because it is error prone and difficult to do quickly. Choose a compass with either a tool adjusted declination or non-tool adjusted. The tool adjusted ones are a little better at holding their setting but either will be fine. 
  • Comfortable in your hand - You want to carry your compass most of the time. Make sure that it is comfortable to hold or has a strap that can keep it in easy reach. My preference is to shorten the strap to a bracelet length so it is dangling near my hand all of the time. I find having it hang around my neck means that it is in the way more often, especially when biking. 
  • Scales on edge - Having a scale on the side of your compass can be handy so that you don't always need to reference the scale index on the map itself when measuring distances. However, with many of today's maps being done with custom scales this feature is getting less useful. 
  • Orienting lines on the dial - It is very convenient having orienting lines on the dial itself. Many compasses will have orienting lines on the base plate but having them on the dial will make your life much easier when you are taking a bearing off of a map. 

What about a mirror?

Why isn't a mirror on my list of important features? Well, it isn't that important. It is true that you can achieve slightly more accurate bearings using a compass with a mirror, however, I don't think it is worth the bother. The mirrored compasses are:

  • Bulkier
  • More prone to breakage (hinges and mirrors)
  • More difficult to use on the move (running, biking, paddling, etc)
  • More expensive
In practice, the accuracy that you will get from a mirrored compass will be reduced to negligible by the fact that you will be traveling over heavy terrain with a limited forward sight line.

So, a mirrored compass is fine, if that's what you have or like, I just don't see the value. Mariners have used non-mirrored compasses for centuries pretty successfully!

What to avoid in a compass

brunton classic compass
Brunton Classic - Low quality compass
Beyond the lack of having the features above, there are a few things you should avoid in a compass. 
  • Surface printed lettering - Unless the lettering is embedded in the material of the compass or sunken, it will rub off. My Brunton is absolutely unreadable after 2 years of use because of the lettering
  • Weird colors - I've found that weird coloring on a compass can make map features disappear in bad lighting. Not a good thing.
  • Gimmicky racing compasses - There are a multitude of gimmicky racing compasses out there. Some don't have any numbering, some strap to your hand or thumb. These might be useful if you are a sprint orienteering racer, otherwise, you probably don't need one of these. It will be woefully inadequate if you need to actually take an accurate bearing.
    Gimmicky race compass
  • Weird shaped compasses - You will see a lot of ergonomic compasses and other strange shapes. Avoid these if you plan on taking a bearing from your map, unless you want to carry a separate protractor for bearing work. 
  • Ultra small - Ultra small is good thing unless it affects functionality. Ultra small compasses are difficult for accurate bearing taking.  


Compass choice is subjective. When you are buying your next compass:
  1. Think hard about what you will use the compass for
  2. Don't get too excited about the latest gimmick. 
  3. Go down to your local adventure store and try a few out.
  4. Buy based on value, not cost.

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