What’s a global compass?

A little known fact about compasses is that most of them function well in only one of five geographic zones.  This is because compasses are balanced differently based on the zone’s “inclination”, i.e., the vertical intensity and direction of the Earth’s magnetic field. 

As a result of these magnetic variances, the compass industry has divided the earth into 5 “zones”, as seen in the map below.

In order to get an accurate reading from a compass, the compass needle needs to be “balanced”, so it does not drag on the top or bottom of the capsule.  But because the differing inclinations in different locations, a compass needle that balances perfectly in North America (zone 1) will drag or stick in, say, New Zealand (zone 5).

To solve this, Suunto (an compass industry leader from Finland) patented a Global Needle that performs perfectly with needle tilts of up to 20 degrees.  This allows a single compass to be used effectively in all 5 of the earth’s zones.

Now there’s no need to purchase several compasses before embarking on your around-the-world eco adventure.  This extra “global” feature adds about $20 to the cost of a compass.

But, what if you’re not a world traveler? Why might you want a global needle?  The global needle’s unique ability to handle tilting makes it perfect for hikers that don’t want to break their stride. Not having to level the compass exactly makes it easier to take an accurate reading while you’re still moving along the trail.
A good global compass model is the Suunto M-3DL, the global version of the Suunto M3 which we Mazamas navigeeks recommend as a great compass for general wilderness navigation.  Read more about why we like this compass at this previous Tip of the Week.

World compass zone chart, courtesy of Suunto: