Choosing a compass

Three different compasses made by Silva. All good in their own way, but each has it’s place.

Your compass is your most valuable navigation tool other than the map itself, so choosing the right one is essential and will make a massive difference to your outdoor activities. You won't appreciate this fully until you have to use someone else’s with different features.

A good compass is an investment that if looked after will last for many years. Indeed, my last one made it over 10 years until the dog bit it in half.

For this post, I will be looking at compasses designed for walking and the outdoors, their functions and various benefits. There are many choices out there which can sometimes seem bewildering, but a basic knowledge of what does what will ensure that you get the right tool for the job.

Essentially, the compass is broken down into two main parts, the base plate (The rectangular bit) and the bezel (the turny round bit). Although obviously, these parts work together, I will discuss them as separate.

The baseplate:

As odd as it may seem, your baseplate must have straight sides. I have seen round and oval compasses which (although excellent for orienteering, sailing etc.) are pretty useless for navigating accurately in the hills. You will need this straight line for working with bearings (which I will cover in a later post) and merely drawing routes on the map.

The baseplate should have a roamer scale. This can take many forms, and some are far more useful than others. The compass (above) on the left has 3 very clear scales for 1:25,000, 1:40,000 and 1:50,000 maps. These scales are on both axes making them very good for giving and receiving accurate grid references. The middle compass has measurements in mm and inches, which I don't find any use at all. You need to be very good at hillside mental arithmetic to get anything out of these which in the cold and rain I am not. The third compass has a roamer on one side in both scales, which, although ok, can get confusing as one can blend into the other when used quickly. This one again has a random bit of ruler printed on the opposite side.

All baseplates need a "direction of travel" arrow. This is the big arrow through the middle. It's surprising how many don’t have this and how much less useful the compass is without one.

Magnifiers are in my eyes (sic) essential. They let you clearly see some of the tiny detail especially on 1:25,000 maps and to read contours and smaller symbols that for most are very difficult with the naked eye, especially in the wind, rain and low light.

Often overlooked is how the numbers are actually put on the baseplate. High-end compasses like the Silva Explorer on the left, have the markings engraved in before being inked in whereas, on cheaper ones such as the yellow one on the right, they are printed on. This looks ok in the shop, but as you can see on this one, it will quickly rub off making the compass a lot less use. 

The Bezel:

The bezel has several essential features, just as if not more important than those on the baseplate. I suppose in a disaster, you could use the bezel without the baseplate, but not the other way round. 

The bezel should be easy to grip and turn in the baseplate, but not so freely that it can move with no input from the user. It should also be useable with gloves as undoubtedly, the time you will need to use it quickly will be in bad weather when the last thing you want to do is remove and try to get back on your soaking gloves. The compasses on the left and right would be suitable for this, but the middle one much less so.

The bearings (in degrees) should be clearly printed around the outside, ideally engraved and inked in like a good baseplate. The centre compass has the problem that the numbers are covered with a layer of plastic. Good when new, but a nightmare when water or dirt ingress making it both hard to read and move. The compass on the right has them printed on and much like the baseplate, they will eventually wear and scratch off. I know people who have been caught out buying bargain compasses only to find they measure military Mils. The measurements are convertible, but it's a layer of hassle you simply don’t need in the mountains as a civilian.

On high-end compasses, the bezel is adjustable for declination, which compensates for the ever-changing difference between grid and magnetic norths. This is very advanced and well beyond the needs of most. I will probably cover this in a MUCH later post.

The Rest:

A much-ignored Part of the compass, but arguably the most important is the needle. This should be fine enough to be accurate but at the same time wide enough to see in poor conditions. As you can see on the yellow compass, the needle is quite fat and thus inaccurate. It is also essential to check for air bubbles in the oil around the needle as this will massively affect the accuracy of your navigation. If your compass leaks oil, most manufacturers (Silva will) cover this under warranty.

In the bezel, you should as a minimum have an arrow that points north, but to be properly accurate, the extra parallel lines make things so much slicker. As you can see, these are completely missing on the yellow compass but fully there on the other 2.

My Compass with the custom lanyard “lark’s footed” around my wrist.

Now, on top of the baseplate and bezel, the often overlooked part of the compass is the lanyard. Quite frankly, the ones supplied with most compasses are useless. They come with measurements on that cant be used in the field and most annoyingly, a quick-release clip to make them safe when put around your neck. When I buy a new compass, the first thing I do is get rid of this and replace it with some fine climbing accessory cord as on the left-hand compass. This cord is very strong with no clip to pop apart, causing you to lose your compass in a peat bog. This lanyard should never be put around your neck, but larks footed around your wrist or a rucksack strap. This way, you can both use the compass safely and efficiently without worrying about losing it. Also, the chord allows you to personalise your compass, ensuring it never "walks off". You'd be amazed by how many compasses I “lost” before I started doing this.

So, the question is, what would I recommend? Well, the best way to get all of the above features would be to look at the common (but officially discontinued) Silva Expedition 4 or the newer and excellent (as I have above) Silva Expedition. The ranger is cheaper, but the roamer scales are only on one axis, making it slightly less efficient. There are also excellent compasses from Suunto and Recta, but they are not as common. Simply put, you pay for what you get. Buy well, and it will be a joy to use. You will see my lovey expedition appear regularly as these posts progress.

Silva Expedition: https://silva.se/product/compasses/outdoor/expedition/

Silva Ranger: https://silva.se/product/compasses/outdoor/ranger/