Evaluating Back-Up Magnetic Compasses

Do you carry a back-up compass when you leave the trail head?  How accurate is it?  This post discusses what your options are.

Frequently in my backcountry land navigation class, I am asked about the need to carry a back-up compass.  Generally students are interested in a light weight model that is low in cost, small in size, and would “fill in” as needed. 

I purposefully evaluated several models many consider to be back-up options.  When choosing a back-up magnetic compass, the hiker must ask himself “What are my priorities?  Is it accuracy? Reliability?  Cost?  Size and weight?”

Different models bring different values to the outdoorsman.   If the primary compass got crushed, misplaced, or stopped working what model would serve as a back-up to get out of the woods safely?  Generally a back-up compass isn’t as capable as the primary.  People want to cut back on weight and expense.
For this evaluation, I selected five commonly used compass models.  They are: the Brunton 9020G, a wrist watch compass “The Navigator” (sold by Country Comm), the Silva Type 3, the Silva Type 7, and a ball compass by Outdoor Product (not Outdoor Research.)

I will compare the five selected back-up units to the highly regarded Silva Ranger (CL 515) and Brunton 8010G base plate compasses to establish a bearing standard. The Silva ranger and 8010G models are oriented to magnetic north as shown below:

Figure 1   The Silva Ranger (left) and the Brunton 8010G (right.)

Neither the Silva Ranger nor Brunton 8010G are adjusted for declination for this review.  This provides a consistent baseline for evaluation purposes. 

To begin the comparison of the back-up compass models, I chose to define them in the categories of (1) reliability (2) accuracy and readability (3) cost and (4) size and weight.

Reliability:

I picked up each back-up compass model option and turned it in place rotating the compass and magnetic needle.   I then stopped and set it on a flat surface oriented to magnetic north.  I quickly found that the Brunton 9020G, and the Silva type 3 and 7 settled quickly and matched the bearing of the standards.  The compass needles quickly aligned to magnetic north and required little movement on my part to stabilize the compass.

The ball and wristwatch compasses were extremely finicky.  Both models required time and manipulation (moving the compass housing side to side, up and down) to get them to align to magnetic north.  Both required what I consider to be excessive movement to level the housing to allow the needle or ball to swing freely.  This was especially true of the ball compass; frustrating.

Figure 2 Compasses from left to right: The Brunton 9010G, The Navigator, Outdoor Product ball compass, Silva type 7 and type 3.  Note that the five compasses close proximity to each other cause the magnetic needles pointing in different directions.

Accuracy and readability:

I then checked the compasses for their alignment to magnetic north.  All models were in general agreement but the three baseplate compasses ( Brunton 9020G, Silva Type 3, Silva Type 7) allowed for a more accurate reading with 2° increments marked on the rotating dial.  Further, each baseplate compass could be used for sighting on a distant object to triangulate the hiker’s position.

The ball compass and the watch compass did not provide for accurate measurement; they just aren’t built for that.  The Navigator has increment tick marks every 10° and the ball compass is marked every 15°.  That said, both will provide a trend of direction. Knowingly choosing a trend of direction verses specific bearing accuracy is a critical choice for the outdoorsman when selecting a back-up compass model.  The impact of providing a trend of direction is that these compasses will indicate that the hiker is moving in a generally northerly direction as opposed to hiking along a bearing of 350°.

Cost:

The most affordable are the ball compass ($2.00) and the Navigator (under $5.00).  The three baseplate models range from $10 to $12.

Size and Weight: 

The wrist watch Navigator is the most compact and is read quickly.  Having a compass on the wrist takes a bit getting used to; it’s just different.  The ball compass is most frequently worn on the exterior of a jacket or on a pack’s web gear.  Both are quickly accessible and are feather light.  

The Brunton 9020G is the largest of the group.  That said, all three baseplate compasses fit easily in a shirt pocket.
Size and weight is of minimal concern for all five models.

The ball compass and Navigator are fine for short day hikes.  Both are good choices as an introductory model and get young people interested in navigation early.

For serious backcountry adventures I’d opt for one of the baseplate models.  The 9020G's ability to adjust for declination is a big plus for me.  The baseplate models are the natural progression for learning the finer points of compass navigation.