How to Use a Map and Compass for Hillwalking in the UK

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A compass is the one piece of navigation kit that never runs out of battery or loses signal. This guide shows how to read your map, take a bearing and follow it, and why it is worth practising on a clear day before you need it in the cloud.

The parts of a baseplate compass

Most walkers use a baseplate compass, the clear plastic type with a rotating dial. These are the parts you need to know:

• Baseplate: the flat edge you use to line up a route on the map.
• Compass needle: the red end points to magnetic north.
• Rotating bezel (dial): marked from 0 to 360 degrees.
• Orienting arrow and orienting lines: these are matched to the map's north-south grid lines.
• Direction-of-travel arrow: the arrow that points the way you will walk.

The Silva Classic is a simple compass of this type, suited to casual walking, while the Silva Expedition 4 adds map scales for 1:25,000, 1:40,000 and 1:50,000, a magnifier and luminous markings. Either does the job described below.

Reading the map

For walking in the UK, the usual maps are Ordnance Survey Explorer maps at 1:25,000 scale. At that scale 1 cm on the map is 250 m on the ground, so 4 cm is 1 km. A few basics help before you pick up the compass:

• The grid. The blue lines running up and down and across the map form a grid. The lines running up the map point to grid north, which is the top of the map.
• Grid references. Read the number along the bottom edge first (eastings), then up the side (northings). A six-figure grid reference pins down a spot to about 100 m, which is what you would give Mountain Rescue.
• Contour lines. Lines close together mean steep ground. Learn to spot hills, valleys and ridges from their shape.
• Features. Look for things you can see on the ground and find on the map: walls, streams, path junctions, buildings and the shape of the land.

Taking a bearing from the map

A bearing is a direction, measured in degrees clockwise from north. This is the method the Ordnance Survey teaches:

1. Line up your route. Lay the compass on the map with its long edge joining where you are to where you want to go. The direction-of-travel arrow must point towards your destination, not back at you.
2. Set the dial to grid north. Hold the baseplate still and turn the bezel until the orienting arrow points to the top of the map and the orienting lines sit parallel to the map's north-south grid lines. Ignore the needle at this stage. The number at the index line is your bearing.
3. Line up the needle. Lift the compass off the map and hold it flat in front of you. Turn your whole body until the red end of the needle sits inside the orienting arrow.
4. Walk the bearing. Look along the direction-of-travel arrow, pick a distant fixed landmark on that line, and walk to it.

Following a bearing

• Hold the compass level and out in front of you, so the needle can swing freely.
• Walk to a landmark, not at the compass. Pick something distinct on your line, such as a rock, a gate or a patch of different ground, and walk to it. Then take the next one. Avoid using anything that moves.
• Do not move the dial once you have set the bearing.
• Check your direction often, especially at junctions and when the ground changes.
• In poor visibility, use shorter legs. Break a long route into shorter stages with a waypoint on each.

The three norths

This is the part that confuses most beginners, so take it slowly. There are three different norths:

• True north: the geographical North Pole.
• Grid north: the direction the map's grid lines point, which is the top of the map.
• Magnetic north: where your compass needle points. It drifts slowly over time.

The angle between grid north and magnetic north is called the grid magnetic angle. When you take a bearing from the map and use it with your compass, you add the angle, and when you take a bearing with your compass and plot it on the map, you subtract it. That is the Ordnance Survey's rule.

In Great Britain this angle is small, and magnetic north has been shifting relative to grid north, so many beginners can ignore it. The value printed in a map's key is only correct at the time of printing. If accuracy matters, for example in a featureless area, you can look up the current figure with the British Geological Survey's magnetic angle calculator.

Working out how long it will take

Naismith's rule is the classic starting point: allow one hour for every 5 km on the flat, plus 10 minutes for every 100 m of climbing. For a group, base your timings on the slowest walker.

Treat it as a minimum. It assumes you are fairly fit, on easy ground and in good weather, so rough terrain, bad weather and rest stops all add time. Many walkers add a margin on top. Start with the rule, then adjust based on how you actually walk.

Common mistakes

• Holding the compass near a phone, a belt buckle or anything magnetic. These can pull the needle off.
• Pointing the direction-of-travel arrow the wrong way in step one, so you set the bearing back to front.
• Not holding the compass flat, so the needle sticks and gives a false reading.
• Setting the dial and then bumping it.
• Walking looking down at the compass instead of at a landmark.
• Not checking the map as you go. Bearings get you through poor visibility, but you still need to tick off features to confirm where you are.

How to practise

1. Start in a park or on a walk you know well, in clear weather.
2. Take a bearing to a landmark you can see, then walk it and check you arrive.
3. Practise giving and reading six-figure grid references.
4. When you are comfortable, try a bearing in lower visibility, with a friend who knows the route.

A navigation course with a qualified instructor is the fastest way to build confidence, and techniques such as aiming off, handrails, pacing and timing are best learned that way. Our hillwalking safety guide covers what else to carry and what to do if things go wrong.

Quick answers

Do I need a compass if I have a phone?

A phone is a useful backup, but batteries run out and signal drops. A compass works without either, so carry one alongside a paper map.

Do I need to adjust for magnetic variation in the UK?

The angle between grid and magnetic north is small in Great Britain, so beginners can often ignore it. Where accuracy matters, check the current value and apply it using the add-or-subtract rule above.

What scale of map should I use for walking?

Most UK walkers use 1:25,000 Ordnance Survey Explorer maps, which show enough detail to spot paths, walls and streams.

Which compass should I buy?

A simple baseplate compass such as the Silva Classic is enough to learn on. The Silva Expedition 4 adds more scales and a magnifier, and suits more advanced navigation.

Sources

• OS: A beginner's guide to using a compass
• OS: A tale of three norths
• OS: Which compass is best for me?
• UKHillwalking: Naismith's rule