Map and compass

Being familiar with a map and compass is fundamental to good navigation.

From a safety perspective, you should not be in the outdoors without having at least the basics covered.

GPS units are fast becoming the favoured option for navigation these days, whether it be in a vehicle, on our mobile phone, or a standalone unit.

However, it’s far too easy to solely rely on them.

GPS is a fantastic thing – and when it works, it’s an easy way to navigate, doing all the hard work for you.

It’s always easier being told where to go!

However, you are relying on a lot of things to get that position or next bearing.

Will the batteries last? Can you pick up enough satellites? Are there trees blocking the sky?

It’s not always a straightforward and guaranteed process.

Added to that, electronics can fail – that’s a fact. And if that’s your only navigational tool, what now?

Objective of this article

The aim of this post is to take a complete novice through the basic elements of map and compass, and clearly explain how they are used in the real world, whether it be for bushcraft, survival or adventure purposes.

This will also be handy for the more experienced among you who may need a refresher – which let’s face it, we all do from time to time!

The low-tech option

A map and compass are low-tech – time tested navigational tools.

They don’t require electronics, batteries or satellites to work and therefore, have very little to go wrong.

If you’re going off the beaten track, make sure you learn some basic map and compass skills at a minimum and be sure to carry them both with you – even if it’s just as a backup.

There’s nothing wrong with using GPS if you want to – just don’t solely rely on it.

---

Maps

There is a lot of information on a map, which can seem a little overwhelming when you first pick one up.

In this section, we will run through the fundamentals and get you up to speed.

Map symbols and what they mean

The symbols, diagrams and all other information that are on your map, correspond to an actual feature or landmark on the ground.

These markings – and what they mean, can be found in the area known as the map key or legend.

It is worth familiarising yourself with these symbols as it will make your map reading more efficient.

You do not need to know them all, as you have the legend on the map close by – and some are self-explanatory – but the more you know, the easier your life will be, as you will not have to constantly cross-reference.

To assist you further, the Ordnance Survey has put together a set of educational flashcards. You can use these to help memorise the symbols and meanings.

See the full list here

How to fold a map correctly

Your map will usually arrive pre-folded, so this part is done for you. The problem arises when you need to get it back that way!

To refold it to its original state, follow the steps below:

Map scales

What does map scale mean?

The scale of a map depicts its direct relationship between a distance measured on the map and the distance that this measurement relates to on the actual ground.

For example on a 1:50,000 map, this means that for every measurement you take on a map, everything is 50,000 times bigger in the real world, hence the scale of 1:50,000.

OS maps are generally produced in one of two different scales – 1:25,000 & 1:50,000.

What does 1 2500 mean on a map?

It means that 1cm on the map, equals 25,000cm in the real world. This is known as 1:25,000 scale.

Using the 1:25,000 scale as an example, a 1cm measurement on the map = 25,000 times that distance on the actual ground.

So if you convert the real-world figure to meters – a 1cm on the map would become 250 metres in the real world (1cm: 25,000cm).

4cm on the map would become 1km (100,000cm) in the real world – and so on.

How big is a grid square on a 1 25000 map?

At 25,000 scale, a map’s grid square is 4cm x 4cm and equals a 1km x 1km square on the actual ground.

What does a 1 50000 map mean?

It means that 1cm on the map, equals 50,000cm in the real world. This is known as 1:50,000 scale.

Using the 1:50,000 scale, 1cm = 50,000cm in the field, is equal to 500 metres.

This equates to 2cm = 1km.

How big is a grid square on a 1 50000 map?

So a grid square on the 1:50,000 scale, is 2cm x 2cm in size, as opposed to the 4cm x 4cm for the 1:25,000 scale.

So, although the size on the map is different, the grid squares represent a 1km x 1km square on the actual ground for both scales. Hopefully, that’s not confusing.

As you can see, the 1:50k map’s 1km grids are smaller (2cm). This means that the map can cover larger areas, which at times has its advantages.

On the other hand, the 1:25k map’s grids are larger, with the total map covering an overall smaller area, but because the grids are larger, the map is ‘zoomed in’ and therefore shows more detail.

The video below is a Royal Marines training aid and helps explain this visually.

Which os map is best for walking

In simple terms, if you want more detail, go for 1:25k scale.

If you want less detail and more ground distance covered on the map – go for 1:50k.

The way I remember this quickly is ‘Less is more’, i.e., the lower number (1:25k) gives more detail than 1: 50k.

Your selection should be based on the situation and preference.

Conversely, in some situations, a 1:25k can actually show too much detail and in doing so, cause the location’s features to become over detailed and less clear.

A 1:50k version of exactly the same section, showing the same feature, although less detailed, can actually be clearer to read – as it is less convoluted.

If you are covering larger areas, such as in a vehicle, then the 1:50k version is probably more appropriate and also means you can take fewer maps with you.

Personally, I like the 1:25k version for outdoor navigation on foot here in the UK.

One of the most popular here in the UK is the Ordnance Survey Explorer range of maps. These come in either the standard version or the Active version, which features a waterproof coating – allowing it to be used in all weathers.

I tend to opt for the standard version and keep it in a map case if the weather is bad.

How to set a map

Setting a map simply means aligning the map’s North, with actual North in the real world.

Do this visually by aligning landmarks on the map, with landmarks on the ground. Your location must be known to do this though.

You can also do this by using your compass. More on this in the compass section later.

Grid references

How to find a grid square

In order to identify a location on a map, you need to accurately pinpoint its location.

This is done in the form of a grid reference. 

On a larger scale, for mapping purposes, the UK is broken up into 100 x 100km squares, or grids.

This is known as the National Grid.

These grids are assigned a pair of letters to identify them as per the diagram below.

Note: The USA, Canada, and many other countries have a very similar system. For this article, we will use the UK system – but the same principles apply – just adapt to your area.

When you purchase a map, you will no doubt have noticed that the map has two letters stamped on it in certain places.

These two letters correspond to one of the areas in the image above that your map is covering.

Your map will likely cover a few different sections of these squares and will, therefore, mention multiple letters in places.

What comes first in a grid reference?

Whichever of these sections you are working off on your map forms the first part of your grid reference. e.g. NH

This way, if you are trying to communicate this grid reference to someone else, they will know which section of the country you are referring to when you state the two letters.

Now that we have established the 100 x 100 km mapping area you are working from, we now need to narrow this down considerably, in order to pinpoint the specific location.

How grid squares are broken down

Now, this 100 x 100km NH section mentioned above, is broken down further into 10 x 10 km squares as below.

You will see these on your map, as the thicker blue lines that intersect at every 10th digit on the map, ie 10, 20, 30…

This has now given us a 10 x 10km (100 square km) area to work in, as shown by the yellow box above.

This is progress, but we still need to get this area down further to achieve any sort of accuracy.

Next, each of the 10x10km squares are broken down further into 1km x 1km grid squares.

Grid squares

How to find grid square

We are now down to the actual grid squares that you see on the map.

These are 1km x 1km wide and of course, give us a total area per grid square one square kilometer.

The red square in the image above signifies one of these squares.

We can now get a reasonable amount of accuracy by simply making reference to this square.

It is still a fairly big area but gives a good high-level indication of where something is located on the map.

We state this by giving a 4 figure grid reference.

How to take a 4 figure grid reference

What are eastings and northings on a map?

Eastings are the numbers that run along the bottom of a map, from left to right.

Northings are the numbers that run up the side of the map, from bottom to top.

How to read eastings and northings

Eastings

Always start by referencing the numbers that run along the bottom first.

These are known as Eastings, as their numbers increase as they travel East.

To help with the correct sequence, remember the adage:

“Go along the corridor, then up the stairs”

So along the corridor = Eastings.

For the red square above, this would give us a number of 97.

Notice how we reference the number at the start of the square (97), not at the end.

Northings

Now we go “up the stairs” by stating the Northing figure.

This equals 18.

We now need to put these two together to obtain a 4 figure grid reference.

This gives us 97, 18.

We are not finished yet though!

As mentioned earlier, there will be multiple 97, 18 grid squares across the country, so we need to signify which mapping area we are referring to.

We do this by adding the area code at the start of the grid reference.

In this example, we are working off map section NH, which gives us a complete 4 figure grid reference of NH 97,18.

By communicating the above, everyone will know exactly what 1km x 1km section of the country you are referring to.

This is how you give a 4 figure grid reference.

How to take a 6 figure grid reference

Knowing where we are within a 1km square is helpful, but for a more precise measurement, we really want to drill down further and get that location within 100 metres of the actual location on the ground.

To do this we take a 6 figure grid reference.

This is done by breaking that 1km grid square down further, into 10 sections, from left to right and bottom to top.

We have our 4 figure grid reference from before of NH 97,18.

This represents the whole of the red square above, but we want to pinpoint the Boat House, so we need to go further still.

As you can see, we need to divide the grid square up further into sections of 10.

You will need to do this mentally, as the grid squares do not go any smaller on a map.

Your compass romer will assist you if this helps. Use the correct romer for the scale of the map you are using. In this case 1:25,000.

We can now locate the boathouse by counting along the bottom first – “along the corridor”.

Then…

Count upwards (“climb the stairs”) to reach the correct square.

In this case, it is 3,3

We now need to add this to the grid squares 4 figure grid ref of NH 97,18 to give us NH 973, 183

This is a six-figure grid reference and is the most common format used for navigation purposes.

Why do we use 6 figure grid references?

A six-figure grid reference is usually the most commonly used type of grid reference, as it gives a decent amount of accuracy for a location.

As above, it gives you an area of 1000m squared, which on the ground is a fairly ‘tight’ area to work with.

However, if you want to get more accurate, you need to break things down further…

How to take a 8 figure grid reference

As mentioned above, a six-figure grid reference is usually as far as you need to go for a good indication of location.

However, there may be times when you need to drill down even further still and provide an 8 figure grid reference.

How accurate is a 8 figure grid reference?

An 8 figure grid reference will give you an area accuracy of 100 x 100 metres – which gives us a total 1000m square area of accuracy.

This tightens things up considerably!

To do this, as you have probably guessed, the square from the 6 fig example above, is further divided into ten each way, to give us another figure to add to our grid reference.

You will again need to do this mentally, and it is a bit tricky to exactly pinpoint it sometimes.

Your compass romer may help, although the numbers are meant for 6 fig references, not 8, so you will need to mentally divide this up.

Example of an 8 figure grid reference

For the location of the Boat House above, we look at where its location is in relation to the smaller square that it sits in.

If we divide this up again – this sits at 4 across and 3 up of the square.

We now add this to our six-figure grid reference to give us NH 9734, 1833

This is how you obtain an eight-figure grid reference.

It’s just a question of drilling down further.

Grid reference quiz

Using the above principles, work out the following (answers at the end):

Question 1

What is the 4 figure grid reference for the waterfall above, highlighted in blue?

Question 2

Now, turn this into a 6 figure grid reference by dividing up the above blue grid square mentally.

We know the waterfall sits inside grid square NN 91,97.

We now need to determine where it sits within this grid square.

What two coordinates do we need to add to make this the correct six-figure ref?

Next example…

Question 3

The above grid square is an entirely fictional HL 15,76 (there shouldn’t be any churches in this region)

Turn this into a 6-figure grid reference, to give the church’s location.

You now should have a good understanding of how grid references work and how to obtain one.

I would suggest you now practice this with an actual map to hone these skills further.

---

The compass

We now move on to the compass and how it relates to navigating with a map.

What makes a compass work?

So, what makes a compass work? Well, the short answer is that the compass has a freely moving and rotating magnetically charged needle, that points to Magnetic North.

This function can then be used to give you a North direction, as well as the others, such as South, East, West and everything in between.

The compass can be used on its own – as well as being able to working conjunction with a map.

As you will see, when M&C are combined, they become highly effective navigational tools.

Let’s explore further…

What are the parts of a compass?

Let’s start with the parts of a standard baseplate compass and what the purpose of each part is.

Compass Baseplate Section

What is the baseplate on a compass?

This baseplate is the main ‘plate’ section, that the compass is based on.

On here you will find:

The direction of travel arrow

This is the arrow that points to the direction of travel. There is also an illuminated line just past this arrow, which shows the arrow’s position at night.

Ruler

Used to help measure distance on a map and provide a straight edge to draw and take bearings with.

Romer scales

What is a compass Romer?

These are sets of right-angled lines that will be marked out in different scales. These being 1:25,000, 1:40,000 and 1;50,000.

These are used to help obtain a grid reference depending on the scale of the map you are using – by dividing up the map’s grid square into 10.

This gives you a more accurate way of obtaining a 6 figure grid reference.

See the map (grid reference) section above for more info.

Magnifying lens

What is the magnifying glass on a compass for?

The magnifying lens is used to enlarge sections of the map to help you read it.

It also has the added benefit of being able to help you start a fire if needed.

See more in our article here.

Rotating bezel section

How to use a compass bezel – compass bezel function.

This is the part that rotates within the baseplate, known as the compass bezel.

This allows you to adjust the angle of the compass against the baseplate which allows you to take bearings, set a map etc.

On this bezel you will find:

Degree markings

These are marked on the outside edge of the bezel, from 0-360 degrees. There will also be North, East, South and West markings on here.

How many degrees are there in a compass?

There are 360 degrees in a compass bezel.

These will usually be marked out as a line for each degree, with a larger marker for every fifth degree and numbered every ten degrees.

Index line

What is the index line on a compass?

This is the marker that the numbers on the rotating bezel match up to – which indicates the degrees figure for your bearing.

Orienting arrow & Orienting lines

What is the orienting arrow on a compass used for?

This orienting arrow points to 360 degrees (North) and gives a reference for the compasses magnetic needle to line up with. This comes in handy when taking a bearing.

These are also straight lines on the bottom of the bezel, that are parallel with the orienting arrow, that are used to line up with the grid lines on the map.

These help when taking a bearing from a map, or transferring one onto.

Magnetic needle

What is the magnetic needle used for?

This is the business part of the compass that points towards Magnetic North.

As you can probably guess the red end with ‘N’ on it signifies North.

Declination scale

Used on an adjustable declination compass to offset the difference between grid and magnetic North.

More on magnetic declination below.

Luminous parts

The key parts glow in the dark to enable you to operate at night.

As you can see in the image, the key parts are illuminated to allow for operation.

What are the parts of a compass – video recap

This video from OS gives a brief visual run-through of the above sections:

Magnetic declination

Compass declination explained

Before we move on to bearings, we need to discuss magnetic declination.

This is the term given to the difference between Grid North and Magnetic North.

In simple terms:

As you can see – they are not the same and are located at different points of the globe.

What is the difference between magnetic north and true north?

Ok, so let’s get this multiple North business out of the way!

As above, there are variations between Grid North, Magnetic North as well as True North.

To be successful in navigation, you need to understand the difference between the three.

Let’s run through them.

What is Grid North used for?

Grid North is what the vertical lines on a map point to. 

The reason for the difference between Grid North and True North is the fact that the vertical lines placed on a flat map, do not perfectly replicate the physical ones that are present on the round Earth.

There is a variation – even though it’s hard to get your head around how this can be the case.

In practice, this variation is very minimal and for most navigational tasks, it can be ignored.

However, just know that there is a difference between Grid N and True N.

What is Magnetic North used for?

Magnetic North or MN is what a compass needle will point to – which is the Magnetic North Pole. 

It differs from True North above, as the magnetic pole field sits slightly off centre to True North.

This magnetic pole also shifts ever so slightly over time.

Due to this, when comparing MN against GN on a map, an offset is manually added in to allow for this.

This is known as magnetic declination or magnetic variation.

How much of an offset depends on how far away the two Norths are between each other, at that point in time.

The magnetic pole is constantly moving and varies from year to year.

Therefore, when you need to transfer a bearing between a map and compass – or vice versa, you need to manually add in (or subtract) the difference.

The current offset is usually displayed on your map and is known as the declination diagram. 

On this diagram, there will be a date mentioned and the offset figure in degrees.

It will state the difference between True North, Grid North, and Magnetic North.

It will also tell you what the variation is each year and in what direction the variation is moving.

What is the definition of True North

True North is the point at the very centre of the top part of Earth, otherwise known as the North Pole.

It is the Earth’s top axis point.

This is also what the North Star’s position relates to – when its position is transferred down to the Earth’s horizon.

For map and compass purposes, you do not need to worry about True North too much – just to have an understanding of what it is.

And now for the video explanation of the above:

Using a compass to navigate (How to use a compass to find direction)

So you have your compass, you have your map – let’s get moving!

Orientation of the map

What is map orientation?

Firstly, it is helpful to orientate your map, so that it is facing the same way as the land in front of you, i.e., North on the map is facing North in the field.

You don’t have to do this, but I find it simplifies things, especially when you are learning.

To align your map, you can use features on the ground, to give you a good idea.

See How to set a map above.

A quicker and more accurate method though is to place your compass on the map and line up the orienting lines with the vertical grid lines on the map so that they run parallel with each other.

The orienting arrow should be facing North (upwards) on the map.

Keep these lines together and rotate the map and compass, until the magnetic needle’s North rests inside the orienting arrow.

Your map is now facing Magnetic North.

How to take a bearing using a compass

Map bearing to compass bearing

Assuming you know where you currently are on the map, you will no doubt now want to navigate somewhere else.

To do this, firstly find where you are and where you want to travel to.

So on the map, you will now have your start and finish point for this particular leg of the journey.

There will be a straight line between these two points – the direction of this line will form the bearing.

We now need to transfer the direction of this straight line between the two points on the map – to the direction between your start and finish points on the actual ground.

Transferring the bearing (convert map to compass bearing)

To get this bearing onto your compass…

Start by placing the compass edge next to your start point on the map – this is your current location.

Rotate the compass, with its side edge pivoting on the start point, until the other end of this edge lines up with your intended finish point.

The finish point should be at the same end as the direction of travel arrow at the top of the compass.

This ensures the direction of travel arrow is pointing in the right direction for where you need to go.

With this lined up and held in place, rotate the bezel until the orienting lines marry up with the vertical grid lines (eastings) on the map.

Once you have done this, adjust for declination if necessary.

Remember, when adding magnetic variance from grid (map) to mag (compass), add the variation on to the bearing.

Now, lift your compass from the map – it’s time to line your compass up with the real world!

With the compass in your hand and in front of you, rotate the whole compass until the magnetic needle’s North sits inside the orienting arrow.

When these two line up, the compasses direction of travel arrow will be pointing where you need to go.

Pick a landmark in the distance that is on this line. This is your direction of travel.

This whole process can be repeated to cover long distances and is how you use a map and compass to navigate.

Transfer bearing from compass to map

If you want to transfer a bearing from the ground onto a map, you do the above in reverse.

This is handy if you can see a landmark, but are not exactly sure where you are on the map right now.

To do this – from where you are standing, line up the compass’s direction of travel arrow with the landmark in the distance.

Now rotate the bezel until the magnetic needle is inside the orienting arrow.

You now have your bearing – which now needs to be transferred to the map.

Adjust for declination – ‘mag to grid get rid‘ – so deduct the current degrees variation.

Now find the landmark on the map and place one of the straight edges, at the top section of the compass on this point.

Now, rotate the whole compass – pivoting the edge on the landmark, until the magnetic needle sits inside the orienting arrow.

Your position is now somewhere on the line that extends down the edge of the compass from the landmark.

How far is for another article where we will cover resection.

This process takes extra bearings from other landmarks to help pinpoint your actual position on the map.

For now, though, you have the basic ingredients for taking a bearing, from map or compass and using it to navigate.

This will get you started on the right foot.

Magnetic compass errors

What can distort a compass?

Metal: Your compass is a sensitive magnetic instrument and can be affected by metal close by.

Be aware of this and don’t use a compass near large metallic objects, such as a vehicle or iron gate, as these can skew the readings by sending the needle off course.

Compass type: it might sound obvious, but make sure your compass is suitable for the region that you are operating in.

That being the Northern or Southern Hemisphere.

Most global compasses will operate in the North, South and Equator regions, but check yours is suitable for the area you intend to work in.

Further info and resources

Mountain Navigation by Peter Cliff

If you would like some further reading on the subject, we would highly recommend the above book, Mountain Navigation by Peter Cliff.

It’s a nice straightforward book to read, without any unnecessary information.

Purchase links: UK | USA | CAN

---

Silva Expedition 4-360 Compass

To purchase the compass mentioned above (Silva Expedition 4-360), you can do so by clicking on the relevant link below.

Purchase links: UK | USA | CAN

---

Where can I buy an ordnance survey map?

To get the relevant outdoor maps for your country, visit one of the links below.

Purchase links: UK | USA | CAN