A compass is cheap, light, doesn't need batteries and works when GPS satellite receivers are blocked by trees and buildings.
They can even be used to orientate a GPS map. Unless the GPS unit has a built-in electronic compass, it will only know where north is when the unit is moving.
Liquid-Filled (Wet) Compass
Liquid-filled compasses are easier to read, especially on the move. The liquid dampens the movement of the needle, making it stop more quickly. This makes them especially good for use on moving vehicles.
However
- The liquid may leak out, stopping the needle from turning. Even a small bubble can cause difficulties.
- Because the case is sealed, problems may arise at high altitudes because of the low pressure (especially if there is a bubble).
- The liquid can freeze if the temperature is low enough, cracking the case.
Air-filled (Dry) Compass
Air-filled compasses are more reliable. Even if the case is cracked, they will continue to work. They are recommended for extreme climates and altitudes.
Water condensation inside the case may be inconvenient, and wet compasses may be difficult to drain dry. But at least the compass should still function.
Needle versus Dial Compasses
The basic compass is just a magnetized needle. The compass rose (north, south, east, west or degree markings) is marked on the compass case. To read the different bearings, the compass case needs to be turned to align the compass rose with the needle.
For convenience, the magnet is sometimes fixed to the compass rose; with both turning together. These dial compasses are easier and faster to read.
Size
Small compasses are light and convenient. However they are
- more likely to fail (suffer a jammed needle), especially the wet ones
- less accurate for taking bearings
Mounting Method
There are different mounting methods
- thumb loop, for orienteering
- paper clip, for fixing to a map
- wrist band, to be worn like a watch
- slot, to be fixed on a watch band next to the watch
- keychain, to be used as a keychain or jacket zipper pull
Accessories
Some common accessories built into compasses
- Declination (magnetic north variation) adjustment.
- Sighting aids. Lensatic (sometimes called military compass) and mirror compasses have devices for accurate readings of the bearings of distant objects. Mirror compasses can also be used for signaling, in survival situations.
- Clinometer (also called inclinometer) to measure slope angles.
- Map-scale ruler, to convert map distances to miles.
- Needle lock. Some dry compasses have a needle lock. Sliding a button stops the needle from moving. This prevents the needle from knocking the case when thrown around, which could demagnetize the needle.
Major Compass Brands
Established brands include Brunton, Silva and Suunto. Basic models can cost tens of dollars.
Embedded Compasses
For convenience, small compasses are often built into hiking and camping equipment:
- Hiking pole
- Swiss Army Knife
- Survival whistle
As these are often small and unreliable, a dedicated compass should also be carried.
Checking a Compass
The compass needle or dial should swing freely in its case. When shaken out of position, it should quickly swing back to point to the north. A sluggish needle indicates a weak magnet, which could soon stop pointing north.
The needle should swing freely even when the compass is tilted. The steeper the tilt it can tolerate, the easier it will be to use in the field.
Carrying a Compass
When in the wilderness, a compass should be worn on the body at all times.
Because compasses can be cheap and light, more than one can be carried to ensure that a working compass is always available.
Resources
- Digital Compass Watch Guide
- Best Emergency Survival Kit
- Best LED Flashlight
- Basic Land Navigation, National Wildfire Coordinating Group
Yuen Kit Mun - Kit Mun is a self-confessed information junkie, reading an average of a book a week over the past two decades. His growing Internet ...
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