How to Use A Compass

How to use a compass is a question many walkers seem afraid of addressing. This section sets our the basics in simple terms. Some think it is complicated. It isn't but like many things in life, practice increases confidence.

The number of call outs to Mountain Rescue Teams is increasing because too many people are relying too heavily on mobile phones for navigation and heading to quite difficult/dangerous terrain with no map or compass. Please spend a little time working through the guidance below.

It is important to be able to use a compass. It could save you from taking completely the wrong route which in itself can be dangerous or the walk could end up being considerably longer than anticipated, perhaps beyond the endurance of you or some of your party. Most walkers start from a parked car and you need to be able to get back to it.

Of course, on a bright sunny day, with a clear path and good visibility with clear visual reference points, you may not need to use a compass. But, what if you are on a featureless hillside or moorland with an indistinct path and/or mist or cloud suddenly descend.

Just as you are right or left handed, you are also right or left legged, i.e. you have a dominant leg. In thick mist with no visual reference points, you will walk a circle - a bit like a rowing boat with one oar. You cannot consciously change this. I have done it myself when I was too lazy to get out the compass and over confident that I knew the way. These are the sorts of occasions when the compass comes into its own.

It is not necessary to spend a fortune on an effective compass. You can get one for under £20. The best known range is probably Silva.

To be most effective in its use, you need to know, at least approximately, where you are. Therefore, use it sooner rather than later.

To state the obvious, the red section of a compass needle points north. In relation to North, at 12 o'clock, East is at 3 o'clock, South at 6 o'clock and West at 7 o'clock. If you never use a compass to any great extent than that, it provides a quick reference at any point, as to whether you are going in roughly the direction you should.

Navigation becomes more accurate when you relate it's readings to an OS map, To make the excruciatingly obvious point, the top of a map is north, bottom south, left west and right east. No doubt you knew that (sorry) ........... but just in case.

On OS maps, you will see the diagram on the right.

Accompanying it will be a statement such as:

"At the centre of this sheet true north is 0º 59' east of grid north. Magnetic north is is estimated at 2º 09' west of grid north for July 2007. Annual change is approximately 09' east.

Magnetic data supplied by the British Geographical Survey."

Already the cries of "gadzooks" or worse no doubt!

In fact, we can instantly reduce the complexity by a third. True north is of no use to us at all. We only care about the grid north (which not surprisingly relates to the grid on the map) and magnetic north (where the compass points).

Forget about true north. We will not mention it again.

We will look at the crucial parts of the rest of the statement shortly but first let's look at a simple compass (simple but quite adequate)

We have a clear plastic base. Along two sides are small rulers to help measuring distances. The clear round "hole" is a magnifying glass (some map print is quite small after all). The black arrow next to the magnifying glass will indicate the direction of travel.

In this case, the black ring (or bezel) is marked at 2º (i.e. 2 degree) intervals, 360º being the complete circle. However, check the intervals on any compass you buy.  Note under the "N" is a small fixed white line, difficult to see on the picture. Just bear this in mind for now.

The bezel is attached to the compass base, the part with the red arrow and the 6 adjacent parallel lines. The bezel turns on the baseplate. The red and white needle is the magnetic compass itself and the red part always points north. 

Returning to the statement, which we will examine in two parts.

"Magnetic north is is estimated at 2º 09' west of grid north for July 2007."

Degrees are divided into "minutes", 60 of them in each degree. In this case magnetic north is 2 degrees 9 minutes west of grid north in July 2007. You cannot meaningfully measure to minutes on a simple hand compass so simply round anything under 30' down and over 30 up, to the next degree.

"Annual change is approximately 09' east."

Although a magnetic compass always points to magnetic north, unfortunately, magnetic north moves, albeit only minutely. The OS note tells you by how much. However, an annual change of this level is tiny and it will be a year or two before we need to round up to 3º . Our adjustment is therefore 2º.  We will come back to this in a minute.

Here is a facsimile of a map which is kept rudimentary so that the grid lines stand out.

Assume you want to get from point A to point B where perhaps there is a footpath but it is indistinct and point B is somewhere in the mist.

Simply lay the compass on the map with its edge along the route you wish to travel, with the large black arrow in the direction you want to go. Twist the bezel so that the lines within on the base are aligned with the grid lines on the map with the "N" of the bezel to the top of the map. As you can see, the needle itself is pointing roughly to the bottom. Don't worry about that. At this stage, it can be pointing anywhere.

The next step is to adjust for the extent to which magnetic north is not aligned with grid north.

If we take a close up view of the bezel, you can see that just to the left of the 60º mark a small but longer fixed white line on the baseplate below the bezel we mentioned earlier.

The small white markings between the 60 and 40 each represent 2º. As magnetic north is 2º west of grid north, we adjust by rotating the bezel one small mark anti-clockwise using the fixed black line on the base as a guide. Relative to grid north, the "N" mark on the bezel and the red arrow (not the needle) are now in the direction of magnetic north, relative to the map.

Now remove the compass from the map, hold it horizontally and allow the needle to point itself to magnetic north and slowly turn the compass until the red of the needle is inside the red arrow on the base.

Now simply follow the direction arrow below, keeping the needle inside the guide on the baseplate..

With a very small deviation of magnetic north from grid north (i.e. only 2º) it is arguable whether it is worth making the adjustment. E.g. just align with the grid lines. Over short distances, this would no doubt be fine. It is only over longer distances that the error would become significant. And, it doesn't hurt to be accurate in any case!

Remember the dominant leg? Well in poor visibility, even following the arrow you could still veer off. It is best to aim the arrow at something, even a tussock of grass or a specific rock some distance away, walk to that, then "take aim" at something else. In this way, your route should remain straight. In the absence of any suitable objects, you could guide a companion to a suitable position, walk to him then repeat.

In theory, if you are lost, you can determine your position by reversing the above process namely, point the direction arrow at a known landmark, turn the bezel until the red of the compass needle is within the red arrow then put the compass on the map with the red arrow aligned north with the grid lines and the side of the straight side of the base against the same landmark on the map. If you do this with a second landmark, where the lines cross will be your position. More accurate is to take three readings. You should be in the centre of the triangle. Once again to be accurate, you could adjust for the magnetic deviation.

The difficult part can be determining a landmark with certainty and it could be impossible in reduced visibility. A mountain you think you know can look different from a different direction. Is the church spire in village A or village B? By far the best option is not to get so lost in the first place, by regular reference to the map and of course by not relying solely on a route from a book.

It may help to orientate yourself if you “set the map”. This term refers to positioning the compass on the map so that its north marking is aligned with north on the map, as follows.

Turn the bezel on the compass so zero degrees or ‘N’ is aligned with the direction arrow on the base plate.

Holding the map flat, align the edge of the rectangular compass plate with the north/south grid lines so that the direction arrow points north.

Keeping the compass in the same position on the map, turn them both so that the red needle lines up with the north/south indicator on the compass. The map will then be oriented with reality and you should be able to recognise the features in front of you.

A term you might come across relating to navigating with a compass is "aiming off". Let's assume that point B on the map below is the corner of two walls, indicated by a black line (as indeed it would be on a 1:25000 scale OS map) and that the corner is crucial to following your route. If visibility was poor and you erred slightly following the compass, you could end up too far north, miss the corner and finish up who knows where. In this case, it would be better to aim further along the wall indicated by the blue dotted line, to be certain of hitting it, then turn left to follow it to the corner.

One tip, it is worth working out compass bearings from strategic points on a walk (e.g. from a trig. point) before a walk and writing them on a piece of paper to slip into your map case. It is much easier and with less chance of error to do this in the comfort of your home/car than in a howling gale with the rain beating down on a mountain top!

Finally, trust your compass. If it is not directing you in the direction you expect, it is not likely to be the compass that is wrong! However, it needs to be kept away from metal objects when you are using it and avoid putting it near anything magnetic, which can (exceptionally) reverse the polarity. It this context, beware any magnetic fastenings on clothing or bags. If there are two of you, it is always worth checking your companions compass too. You have more chance of winning the lottery than two compasses being wrong!

If you are flush with cash, a GPS receiver can not only tell you exactly where you are but also do the entire navigation for you. Do bear in mind that they need a clear view of the sky so can be ineffective under heavy tree cover.

Using Map and Compass Reading List

Visit the Happy Hiker Hiking Store to buy compasses.

All information on this site is given in good faith and no liability is accepted in respect of any damage, loss or injury which might result from acting on it.