The Brunton TruArc 10 is a baseplate style compass with a declination adjustment that is best suited for use in forested or mountainous terrain where you can rarely see your destination. Featuring a global needle, you can also use the TruArc 10 compass interchangeably in the northern and southern hemispheres without having to buy a new compass, since most are calibrated to one hemisphere but not both. This is handy if you travel above and below the equator for hiking or mountaineering, but is just a nice-to-have if you don’t.
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, 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 bezel will read 344 degrees instead of 360.
While the Brunton TruArc 10 has a declination adjustment, Brunton inexplicably goes out of their way to hide that fact from you in their product packaging and online product descriptions. It’s rather bizarre. I had to literally buy the compass to find out.
Further, the directions that Brunton provides for setting the declination on this compass are very difficult to understand, even though the declination adjustment is tool-less and quite easy to set. For your reference, grasp the top edges of the clear plastic housing on top of the bezel ring and twist them it while holding the bezel stationary. This will move the declination needle and let you set it to the correct offset value.
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 is 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 also helpful to get a compass with long baseplate edges, not just for reading bearings but for marking up your map if it doesn’t have pre-drawn north-south grid lines. Drawing these lines in with a pencil makes it easier to align the north-south lines inside your bezel with the north-size lines on your map (shown below.)
While the TruArc 10 has a straight edge on the right side of the baseplate, it has a curved handgrip on the left. While this is more comfortable for carrying, at least if you’re right-handed, it makes it impossible to align the straight edge of the base plate with a drawn direction of travel line when the line is near the top border of your map, while still keeping the bezel over the map. See the photo below.
If you can’t position the north-south lines inside the bezel over the north-south grid lines on your map, you can’t read an accurate bearing off the map. I find this pretty annoying, although I suppose you can reprint your map to get around it if that’s an option.
Degree of Precision
The degree of precision, or space between the tick marks on the Brunton TruArc 10 bezel is one degree, which is pretty impressive for such an inexpensive compass. The TruArc 10 also includes a built-in magnifying glass positioned over the bezel so you can still read it while you hold the compass at arm’s length.
It’s also more than enough (two degrees of precision is also perfectly sufficient) for navigating overland, where a plus or minus three degree variation off of a bearing can be expected as you weave around boulders, stream beds, and other natural obstacles.
While the Brunton TruArc 10 baseplate compass has a few quirks, it’s actually quite a good value for a tool-less declination adjustable compass. While a global needle and 1 degree of precision are not strictly necessary for most off-trail hikes, they’re nice value ads that extend the utility of the product. My only caution is the terrible documentation that Brunton provides with the TruArc 10 for adjusting the declination since it’s extremely difficult to figure out without assistance. Hopefully, the directions I’ve provided in this review remedy that so you can use the TruArc 10 to good effect.
- Tool-less declination adjustable
- Global needle
- Poor product documentation and instructions
- Lack of a second straight edge
Disclosure: The author bought this product with his own funds.
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