Suunto M3 Compass – A Review

Having recently graduated the Army Mountain Warfare School’s Basic Mountaineering course I was introduced to a newer, and, in my opinion, more effective type of compass.  Being fairly proficient at land nav already, I found it even simpler after having been shown how to use the Suunto M3 compass.
A pretty simple device that nearly eliminates the use of a protractor by combining measuring and azimuth features together into one package, the M3 has some amazing additions that help to eliminate the error produced by converting grid to magnetic when navigating.  Anyone who has ever been out trying to get a resection knows, that can quickly run them afoul and lead them a good distance off course.  wp-1467067110082.jpeg
As you can see from this picture the lanyard comes with a key attached.  The key is for the purpose of spinning the inner bezel and being able to set it to the natural declination of the area in which you are operating.  As you can see in the above picture the red “shed” arrow is pointing straight in line with the direction of the compass.  For the purpose of this post we will be using a map of the Fort Richardson / Anchorage area as seen below.


And as such, the declination of this particular area is 25.1 degrees as you can see here.

Now typically, as you can see, you have to ensure you are doing the proper conversion from grid to magnetic or magnetic to grid appropriately.  However, you eliminate doing so by pre-setting your M3’s declination.  Your magnetic azimuth will always be set to match your grid azimuth.


To easily set the declination you place the center of the compass over the cross section of the declination chart; aligning North on the compass with GN (grid north) on the map.  From there you turn the inner bezel with the key (NOTE: it doesn’t unlock the ring to rotate as I initially thought, but rather actually turns it like a gear) until the red “shed” is aligned with the magnetic north as shown above.  It can be a very deliberate process to get it set properly, but using a very fine touch will get you on target.  From here, like any other land nav, you mark your points on the map.  This, while possible to do with the compass itself, is the one time you may actually want to use a protractor.  If you have known points like these, Wolverine Peak, and Little O’Malley Peak, you won’t even need to use the protractor at all.  However if you are going from a known grid it could take a little more individual practice to line up the measure to get your grid right.  Forewarning, count your hash marks before assuming you’re right.

As you can see I also took the liberty to mark the elevation of the points too.  I will touch on this more at the end, but when operating in mountainous terrain, the elevation can take some of the guess work out; resection can be 3D, not just two 2D points.


Once you have your points marked use the edge of the compass to line up your points with the red triangle seen at the bottom pointing in the direction of travel.  If you found you went the opposite way and had your red triangle pointing to your start point, no worries, you can just use your back azimuth (use the black arrow to navigate) instead without needing to readjust.  Once you have oriented your compass to the direction of travel, you will then need to turn your outer bezel and align the red grid lines inside to the grid lines on your map.  In the above picture they are aligned in relation to the photograph; below the photo is off center to show the importance of getting the right perspective to the compass in lining up the compass grid with the map grid.

Once you have aligned the grids, all you have to do to travel in the direction of your next point is to point the red triangle in front of you and turn until you place the red arrow “Fred” into the red “shed”.  Keep Fred in the Shed and just walk.  Simple stuff.

As I mentioned earlier, using a 3D resection to determine your exact position comes in pretty handy.  To do this, however, you will need an altimeter.  Altimeters measure air pressure to determine the elevation you are at.  They come in analog and digital, both of which I’ve used and both can prove to be highly accurate.  Keep in mind though as you use these over time, the change in weather patterns can have an effect on them.  That being said, verify your elevation every time you reach a known point in case a low or high pressure system has moved in over time.  For the Basic Mountaineer course we were provided Suunto watches which had an altimeter function.  I came with my own G-Shock Rangeman and was able to compare the two during the course.



Shown here is my G-Shock Rangeman, which ultimately I preferred.  I found that through the course the Suunto was more likely to be off by up to 10 meters in elevation.  The Rangeman was usually no more than 2 meters off, which could easily be attributed to changing weather patterns.  The Rangeman was also a lot more user friendly and easy to navigate through options like changing from feet to meters (which its important to note what measurement your map uses before hand; 1300 ft and 1300 m is a big difference when you go scaling up the side of a mountain).

Some other additional features of the M3 which I didn’t get to discuss yet are that it as a luminescent dial.  Which, while not tritium, is still handy for traveling during low light.  It has measurements for each grid size for maps, as well as standard and metric (make sure you’re looking at the right one, I initially started measuring in miles instead of meters myself).  The compass also comes with an embedded magnifying bubble.  I think that’s pretty self explanatory, as I’m sure if you’ve spent 5 minutes looking at a map, you’ve looked at something on there and said to yourself, “what the hell is that?”

Ultimately, using either or these devices discussed independently or in conjunction can make navigating a relatively simple feet.  I was able to complete all 5 points with a walking distance of 13 kilometers through mountains with time to stop and have a snack.  It wasn’t the star course by any means, but accurately finding your points can make the difference of strolling or running on a course, and being alive or dead in a real world scenario where someone wants to kill you.  You can practice marksmanship and tactics all day, but if you don’t know how to get to where the enemy is you certainly won’t be able to shoot them.

Food for thought.