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If you’re venturing into the hills you’re going to need a compass, after all, moss grows wherever it’s favourable for moss to grow and you can’t rely on seeing the Sun. The following serves as a guide to compasses suitable for land navigation, the features you need, the extras you might not, and what you get for your money.


As with watches, the things that set a quality compass apart from a cheap one are the mechanism and the quality of construction. A quality compass will settle on north smoothly and quickly and be of suitably robust construction, from a manufacturer willing to offer a warranty. However tempting it may be to make a saving, a cheap compass will almost certainly fail on you. Look to spend at least £20, tick all the boxes above, and take care of it as you would life-saving PPE.

The Silva Expedition and Silva Ranger compasses are the workhorses of the outdoor industry. Both are available to buy when attending a course at Pure Outdoor, or via our website.

Figure 1 The Parts of a typical compass

First, let’s look at the things you definitely need in a compass:

1. A transparent baseplate that functions as a protractor. Not a maritime compass, one that can be placed flat on the map leaving the map visible beneath. The baseplate should be short enough to fit in a pocket and long enough to enable you to take a bearing. Rubber friction feet add stability when taking bearings in the field.

2. A Magnifier. Indispensable in poor visibility and complex terrain.

3. Measurement Units: As a minimum: Easy-to-read metric ruler, degrees and romers at appropriate scale(s).

4.  Large enough to read and operate in the field when wearing gloves. A large bezel with a rubber grip is useful on wet, wild days. Novelty, button compasses are inadequate.


Figure 2 Maritime Compass, unsuitable for land navigation
Figure 3 Novelty button compass: Inadequate


In addition to the above, manufacturers offer numerous other non-essential features which may be useful depending on your needs. These are described to help you make an informed choice and decide whether to spend extra cash.


Mil Compasses

‘Mil’ compasses (mil being short for milliradians, 1 degree being equal to 17.453mils) are favoured by militaries due to their range-finding applications. While no more or less accurate than conventional compasses, most will show degrees only on the inside of the compass housing, making degree bearings trickier to read and share in the field. Be sure to check the compass bezel before purchase as some retailers mix stock.


Figure 4 A 'Mil' Compass. Milliradians on the bezel, degrees in the housing

Declination Scale

A Declination Scale in the compass housing is used for overcoming Magnetic Variation. Grid North (North on your map) is slightly different to Magnetic North (the North your compass needle points to). This is due to the need to produce consistent mapping despite the inconsistency of the Earth’s Magnetic Field, which causes the magnetic pole to move around. As a navigator it’s important therefore to know and account for the degree of difference, the Magnetic Variation (aka Declination). Magnetic Variation is expressed in degrees East or West of Grid North. At the time of writing, magnetic variation at our Peak District base, The Adventure Hub (located at National Grid Reference SK 205 826) is 1 degree West of Grid North. To account for magnetic variation we therefore must correct 1 degree East by adding 1 degree to any bearing taken from the map in our locale. Usually we calculate this in our heads and make the necessary adjustment. With a declination scale the compass can replace the mental maths:


Figure 5 Compass housing showing West/East Declination Scales


In our example, Magnetic North 1° West or Grid North. Take your bearing from the map. Hold the compass flat and turn yourself until the red end of the compass needle points to 1° on the “W.decl.” scale. Keep the compass steady and turn the compass housing until the North arrow aligns with the red end of the compass needle. Its usefulness is debateable, however some more expensive models offer the ability to fix the declination in place with a supplied key, handy in hostile environments with significant magnetic variation.


Clinometer

Some compasses have a second needle inside the housing, a CLINOMETER, used for measuring the inclination of slopes (or sloping surfaces) in degrees, using the same scale as the Declination Scale shown above. Hold the compass on its side and the clinometer needle will point downwards like a plumb line. Hold at eye level, sight through the baseplate and tilt the compass to align with the terrain or whatever surface you wish to measure the incline of.

Figure 6 A Clinometer

Sighting / Mirror compasses

Using a Sighting compass helps maintain accuracy when following a bearing in the field. However, the additional moving parts and mirror add weight, bulk and expense and reduce robustness. To use a sighting compass with a mirror, take your bearing from the map as normal, then hold the compass at eye level with the mirror tilted to a 45° angle. The mirror enables the navigator to simultaneously sight the bearing in the terrain while confirming that the compass needle is aligned with the North arrow in the compass housing. (And if it comes to it you can use the mirror for grooming or to signal for help. Use your outstretched hand or foot to help aim the reflected light where you need it.)


Figure 7 A Sighting Compass in action

Fluorescent / Radioluminescent Elements

Some compasses boast glow-in-the-dark Needle, Housing and Direction of Travel Arrow to aid night navigation. The luminous compound applied needs to be activated by daylight or flashlight and will fluoresce for up to 4 hours.

Radioluminescent compasses, containing the gaseous radioactive isotope Tritium, emit continuous light for approximately 7.5 years, with no need to ‘recharge’ with external light. Such compasses are not widely available and, though safe, come marked with a yellow radiation symbol.


Figure 8 Tell-tale red text and radiation indicator of a radiolumiescent compass.

Global Compasses

If you intend to travel to latitudes south of the equator, consider buying a global compass, essentially a compass with larger housing which enables the needle to move vertically as well as laterally. The closer you are to the south pole, the greater the downward force on our compass needle. The larger housing helps overcome this, preventing the needle from dragging on the housing and impairing function.

An experienced mountain skills coach, road cycling guide, caver, climber and fell runner, Stephen instructs navigation and mountain skills year round and has led countless mountain challenges and expeditions throughout the UK and Europe. Always cheerful in the face of adversity, and with a taste for the epic, Stephen achieved a long-held ambition by completing the Bob Graham Round in June 2015 - loving every minute of it!

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