Brunton TruArc 10 Baseplate Compass Review

The-Brunton-TruArc10-Compass Review
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?

Declination Adjustment

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.

The Brunton TrueArc10 baseplate compass declination adjustable - set here to 14 degrees West
The Brunton TrueArc 10 baseplate compass is declination adjustable – set here to 14 degrees West

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.

Your map's declination is usually located near the map scale. This one is 16.5 degrees west.
Your map’s declination is usually located near the map scale. This one is 16.5 degrees west.

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.)

Once you've adjusted for declination, you can read your brearing straight from the compass by aligning the vertical lines in the bezel with north-south grid lines you've drawn on your map
Once you’ve adjusted for declination, you can read your bearing straight from the compass by aligning the vertical lines in the bezel with north-south grid lines you’ve drawn on your map.

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.

It's difficult to use the TruArc 10 for calculating a bearing when the drawn direction of travel forces teh bezel off the top of the map
It’s difficult to use the TruArc 10 for calculating a bearing when the drawn direction of travel forces the bezel off the top of the map

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.

The Brunton TruAc 10 has 1 degree of precision and includes a magnifier so you can read the bearing more easily
The Brunton TruArc 10 has 1 degree of precision and includes a magnifier so you can read the bearing more easily

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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  1. Great review Philip. I was wondering how long you have had the Brunton? I noticed you have a decent sized bubble in the rotating housing. I know that all modern liquid filled housings tend to acquire them over time. Has this bubble grown at all since you first noticed it?

  2. I’ve been using this compass for several years. It was formerly called the Brunton Eclipse Adventure Racing Compass, primarily for orienteering. I especially like the map grid tools built into the base plate, which is very handy for SAR. Instead of juggling a compass and separate map grid tool while holding a map in the field, I just have the compass and map. Initially I was concerned that the grid printing on the bottom of the base plate would wear off, but that hasn’t happened yet in 4 years of use.

  3. I replaced a very old Silva with the Brunton TruArc 5, which is a good basic compass, and I was given a TruArc 20 fthis past Christmas, which is quite a bit more compass than I’ll ever need. The instructions that came with both of them are just plain awful, but especially those for the TruArc 20. I’d greatly appreciate a review of that one, but it might test your patience.

  4. Don’t forget that the declination adjustment value printed on the map is only correct for when the map was printed. If your maps are at all old (I use some topos from 1953 in areas of little change) the declination value is likely to be off by a few degrees. Web search for NOAA declination get current values. That big glob of magnetic north pole is constantly moving.

  5. Great review, thanks. I have the Brunton-F-BOSS70M-Mirrored-Baseplate-Compass, and I cannot see where to set the declination and this is a tool free declination compass. I no longer have the instructions. Are you familiar with this compass and how to set it?

  6. Your compass is defective – it’s not supposed to have a bubble in the capsule! This is very concerning to me, because I owned the two predecessors to the TruArc 7 – the 8096 AR and the OSS 40B and they both developed bubbles that grew to such size that they impaired the action of the floating dial.

    Brunton seems to have given up on the circle-on-circle system and gone back to a traditional needle, except for using stronger rare-earth magnets like the orienteering racing compasses use (Silva Jet, Suunto Arrow 30, etc.) for faster damping. Definitely an improvement.

    One thing I could not tell from your review was whether or not the needle is gimbal-mounted like the Suunto and Recta global needle compasses – is it? I imagine the Recta/Suunto patents have run out by now.

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