The Suunto M-3 D Compass is a baseplate style adventure compass with a declination adjustment that is optimized for use in forested or mountainous terrain where you can rarely see your destination. I’ve been using mine for 4 years, ever since I became really interested in off-trail hiking and navigation and started teaching those skills as a instructor for the Appalachian Mountain Club.
There are three things that I look for when evaluating a compass for personal use:
- Does it have a declination adjustment?
- Is it a baseplate compass?
- What is the degree of precision on the bezel ring?
A declination adjustment lets you navigate using map north (also called true north), instead of magnetic north. This means that you never have to add or subtract degrees to bearings when translating between the map and a bearing that you want to follow on your compass or from the field to the map. Adding and subtracting declination adjustments is a huge source of confusion and errors, for beginners and experts alike, that goes away with a declination adjustable compass.
With a declination adjusted compass, the needle of your compass still points to magnetic north, but the bearing on your compass bezel is offset using the declination marked on your map, so that the number of degrees that you read off the bezel factors the declination in, without you having to add or subtract degrees in your head.
Let’s say your declination is 16 degrees west (you find this on your map). When you face north and point your compass to magnetic north (put red in the shed), the bearing on your compass will be 344 degrees instead of 360. It actually doesn’t matter what direction you face, because the declination adjusted bearing will always be offset by those 16 degrees west, when you put red in the shed.
Baseplate Style Compasses
The straight edge sides of a baseplate style compass are essential for plotting bearings on a map. Without a straight edge, it very difficult to draw a line between your current location and your destination and read the required bearing off the compass. It just introduces too much undesirable error.
It’s very helpful to get a compass with the longest baseplate edges you can find, not just for reading bearings but for marking up your map if it doesn’t have true north lines drawn on it already. Drawing these lines in with a pencil make it easier to align the north-south lines inside your bezel with the north-size lines on your map (shown below.)
Degree of Precision
The degree of precision, or space between the tick marks on the Suunto M-3 D bezel is two degrees, which is more than adequate for navigating on foot. If you’re careful, you can position the bearing mark at the top of the between the tick marks, giving you one degree of precision. A compass like the Suunto Clipper which has 10 degree increments is completely useless for point-to-point navigation and I wouldn’t recommend using it for that purpose.
I’m a big fan of the Suunto M 3-D Compass because it is easy to use for quick and dirty as well as finely, detailed and calculated hiking navigation. This compass has taken me to some pretty wild places, here and abroad, and never let me down. Declination adjustability, a baseplate, and good precision: those are the key features I look for in any compass, and the Suunto M-3 D delivers.
Disclosure: The author bought this product with his own funds.
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