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How to use a map and compass

How to use a map and compass

I spend my days either teaching outdoor skills or guiding people in the great outdoors. It would take a lot for me to be convinced that I don’t have the Best Job In The World ™. I have been doing it for nearly a decade and I still get a real buzz from sharing my knowledge and experiences with clients, and finding out about their own skills and backgrounds. Any instructor worth his or her salt will agree that you never stop learning about your subject – whether it is polishing your own skills or discovering new ways to deliver those skills to your students.

Navigation in SnowdoniaSomething I will never forget is one of my first solo mountain trips. I was 18, fresh from my A Levels and ready to conquer the world – well, a shop assistant in the local supermarket, but you get the idea… I was invincible. I could walk 20 miles in a day without a problem, scamper up overhanging rock routes and sleep on a wafer-thin mat on a pile of lumpy rocks. I had long hair and a beard and was doing a reasonable job as a boy pretending to be a man. I also believed that I already knew all there was to living out of doors, and happily set off for a couple of days across the Rhinogs, a rough and remote mountain range in the southern half of Snowdonia.

I had all the kit I thought I needed, all carefully chosen within my meagre budget, and dutifully packed a paper 1:50,000 map of the area and a compass. The sun was shining, the weather warm and I had miles of trackless mountain exploring ahead of me.

Only this was Wales, so it was going to rain. And tracks are very useful for travelling through the mountain vegetation. And I really had no clue what I was doing.

As the heavens opened the visibility dropped and I lost confidence in my position. I resorted to getting the map out, and for the next 30 minutes watched it gradually turn into papier mache as the rain saturated the uprotected map. I had a compass, but didn’t know how to set a bearing let alone use it to find my way back to safer ground.  I was in trouble…

How to use a compass with a map

Here in the UK we are lucky to have some of the best topographical maps in the world. I have found better maps elsewhere, but the I have also seen elsewhere in the world have a fraction of the detail that the Ordnance Survey maps do, and often the detail that exists is of dubious accuracy. However, as long as you have a reliable map and a good working compass you can use it to find the grid bearing from one location to another, set it on the compass and then follow it on the ground.

  1. Lay the baseplate of the compass flat on the map so that the edge goes between your position and the destination.

    Lay the baseplate of the compass flat on the map so that the edge goes between your position and the destination.

    Once you have pinpointed your location on the map, and found the feature you want to navigate to then you can ‘set’ the compass bezel to the Grid Bearing. To do this, you place the baseplate of the compass on the map (kneeling and holding the map on your horizontal thigh is an excellent way to ensure you keep it level), with one of the long edges touching both your current location and your destination.

  2. Now, without moving the baseplate, gently turn the bezel of the compass until the lines on the clear underside of the bezel are parallel to the Northings on the map – making sure that you are lining up the ‘North’ symbol on the bezel with the top of the map!
  3. There is a small mark or line at the 12 O’clock position on the bezel – the number that you read here is your Grid Bearing.
  4. Now pick up the compass and hold it level in front of you, close to your chest where you can look down on it from directly above, and away from any magnets or large metal items (including mobile phones, zips, cameras etc) that may affect the magnetic needle.
  5. Now rotate the bezel until the lines are parallel to the Northings on the map.

    Now rotate the bezel until the lines are parallel to the Northings on the map.

    If it is required, make a small adjustment to the bezel position for any magnetic (the difference between the Magnetic and True North poles) deviation to get your Magnetic Bearing. This is very important as it can be as much as 20 degrees depending on your location. In the Western UK at the moment it is around 1 degree, but the magnetic deviation is changing over time. Consult local maps and other sources for the figure you need to adjust for.

  6. Now, with your Magnetic Bearing set on the compass stand with your feet at shoulder width apart, your hips and shoulders straight and the compass held level at your chest. Rotate your entire body whilst looking down and align the magnetic needle (usually with a red tip to mark the ‘North’ end of the needle) with the marks on the base of the bezel and the ‘N’ symbol.
  7. When you have done all of this and the compass is lined up just lift your head and look straight ahead – you are now looking directly down the line of that Magnetic Bearing. Find a distinctive feature on that imaginary line and then walk towards it. Make regular checks with your compass to ensure that you are maintaining that bearing, and that you do not wander left or right.

To take a bearing from the ground and plot it on the map the process is pretty much the same, but reversed:

  1. Find the object you wish to take a bearing from and line your body and compass up towards it as before
  2. Once your body is in position, turn the bezel on the compass until the red needle end lines up with the ‘N’ symbol.
  3. Make any adjustments for Magnetic Deviation – this will be the opposite of the process above, so if you add 3 degrees when converting a Grid Bearing to a Magnetic Bearing, you need to subtract 3 degrees to do the opposite.
  4. Now place the compass on the map and turn the entire compass (not just the bezel this time) until the compass is lined up with the Northings as before.
  5. You can now see where that bearing lies on the map.

With practice you should be able to do this process in a minute or less – and having the confidence in doing it accurately everytime is one mark of the true outdoorsman or woman. It is a skill we should all practice, especially if you don’t get to use it ‘for real’ very often as the skills do start to get rusty and we may start to forget some of the important steps.

A good exercise to practice these skills is to try and locate objects on a map using a process called triangulation, or more properly Resections and Intersections. A Resection is used when your position is unknown using two or more known distant objects, and an Intersection is used to find the position of a distant object from two or more know places.

how to take a resectionResection

If you do not know your location, but can see two or more distant objects and you can find them on the map (e.g. a church tower, a distant summit or a farmhouse) then you can take Magnetic Bearings of these objects, turn them into Grid Bearings and then draw those lines on the map from those known places. These lines will intersect, usually in a triangle for three bearings, and your position will be somewhere within the centre. This is very useful in open terrain when surrounded by hills and you can identify the summits.

Intersection

This is a similar process, but instead of standing in between three know places and taking bearings, you stand AT the known places and take a bearing of a distant unknown object. This is the way that fire towers in forested wilderness areas work – rangers can each take a bearing on a distant forest fire and by combining two or more bearings they can locate and direct resources to that fire.

So what happened to me in the Rhinogydd, stumbling through the heather and boulders with a mushy map and a growing sense of humility? Well I got lucky – I hit a very distinctive path known as the Roman Steps and followed it down to a campsite by a lake. I pitched my tent and took stock of the situation – my planned adventure was pretty much over, so the next day I followed the road down to the coast and hitch-hiked back around to my car. That night I dug out an old copy of the legendary ‘Mountaincraft and Leadership’ by Eric Langmuir and buried myself in the navigation section. Over the next few months I taught myself how to navigate properly, and honed and polished those skills through more adventures in the UK and overseas. I used waterproof map cases in the future, or bought laminated maps that were totally rain-proof. It didn’t mean that I was never lost again – but I now had the skills and means to relocate myself when I had become ‘geographically misplaced’.

Using a compass properly is not the only vital skill a navigator needs, but it is one of the cornerstones of navigation that safe outdoor travel is built upon. Carrying a map and compass is very important – but unless you know how to use them they are just something else weighing you down.

Learn how to use them and set yourself free.

You can find out more information and learn to navigate with Richard on one of our navigation courses in the UK.

Glossary of Terms

Baseplate – the flat, clear plate on the base of a compass. Normally has a ‘Direction of Travel’ arrow on it – this points towards the object you wish to navigate to or have taken a bearing from.
Bezel – the moveable part of the compass, normally with markings for 360 degree or 6400 mils. The civilian world works almost exclusively in degrees.
Needle – Magnetised needle that aligns on Magnetic North/South. The ‘North’ end is normally marked in red.
Grid Bearing – The bearing taken directly from a map
Magnetic Bearing – The bearing followed on a compass, adjusted for local Magnetic Deviation
Magnetic Deviation – The difference between Magnetic North and True North as marked on maps and is vital for accurately following a bearing. This varies across the globe and with time – consult local sources of information.
Resection – Method of location using converging bearings from two or more known distant points.
Intersection – Method of identifying distant unknown object location using bearings from two or more known points.
Northings – The lines marked on the map showing where True North is. These are usually the vertical lines – the horizontal lines are called Eastings.
Coastal Foraging Course Report May 2015
The Importance of Being... a navigator

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