How To Use A Map & Compass
Words by: Jason Rawles
Use The Right Map
There are loads of different maps out there but pick one type and get familiar with it. For pretty much everything, I use the Ordnance Survey 1:25,000 scale maps. On each map, there is a ‘legend’ as in a list of what the symbols, colours and lines mean.
Get familiar with it and how to orient it. To orient the map is to move it around (with it open and flat) so that the symbols and features are all in relation to the ground around. The other easy way to do this is to use a compass so that the North on the compass needle is also aligned with north on the map.
Find somewhere you know and practice. Once you have this down, you’ll be confident in navigation across unfamiliar terrain.
Get To Know The Compass
A compass is a complex looking beast but it works on simple principles. In its simplest form it helps point towards North and then you can orient your map. Using it in its full capacity will help you measure distance, timings and give you right direction in poor visibility. This is a great article from Ordnance Survey about using a compass.
Make sure that when you use it you’re not near big metal objects or things like your phone. Hold it away from your body. Also, store it away from these objects as this could cause it to reverse its polarity which means the needle will point south and not north!
Plan Small Legs Within Bigger Routes
A route, for example, would be a day out - so you start in one place like a car park, walk around for a period of time, then finish either at the same place or somewhere else. When you’re planning an adventure using a map and compass break the route into sections which are called legs. Breaking down the adventure down into legs makes it easier to plan and manage.
Ordnance Survey via OS Maps have over a million routes that are already created but you need to break it down into smaller and more manageable chunks. By chunks I mean sections and that could be something like:
- Start at the car park
- Walk to the lake
- Turn right when you get there and get to a road
- Turn left at the road
- span>>Turn left at the big bend in the river
- Walk for 30mins back to the car
- Eat cake
It’s less daunting to have 7 small sections than one big route.
Distance & Timings
This is a very simple calculation. When you walk at a steady pace you walk 100 metres in around 1.5 minutes. That means to walk a kilometre it takes roughly 15 minutes. If you walk uphill, it takes longer and on rough ground, it can slow things down.
When you look at an Ordnance Survey map you’ll see it has squiggly lines on. These are called contour lines. They represent how steep the ground is because you’re looking at a map in 2 dimensions. This helps visualise how steep the ground is. Contour lines close together indicate steep areas and lines that are further apart show gentler gradients.
On most 1:25,000 maps the contour lines are 10 metres apart in vertical height gain but on some, it could be 5 metres. Do check.
Each grid square on a map is 1 kilometres in real life; so now we know if you walk that distance it will take 15mins.
If you walk uphill and the map shows 5 contour lines, it is 50 metres of height gain. Let’s add one minute for each contour line.
15mins distance + 5mins height gain = 20mins walking in real life
Some of this may vary from person to person but it’s a decent rule of thumb.
Now you have some way of planning a route based on how much time you have, how fit you are and how much steep ground you aim to covered.
Using Grid References
When you look at the map you’ll see a set of numbers on the bottom and a set of numbers on the left. This is assuming you’re looking at the map with north pointing upwards.
With these numbers, you can pinpoint a location with a reference; you may have heard these called out in various action movies. While you may not be calling in an airstrike to an enemy location you may have to tell someone where you are in the event of an emergency.
Also, because there are so many maps that cover the UK each map has its own unique two-letter code, something like SH or TL. This is detailed in the legend.
So, to explain…
- The first number you need to work on is the bottom number. Think of it as building the foundations before putting the walls up. Along first and then up or even along the corridor and up the stairs.
- Find a symbol you want to work with within a grid and then find the number along the bottom of the grid it’s in. It will be to the left of the grid and could be something like 6.
- Then find the number of the grid on the left (vertically) on its way up and it’ll be the number at the bottom of the grid and could be something like 3.
- Therefore, the grid reference for that whole grid would be TL63; and that’s right, you guessed it, it’s for the whole grid which is 1km x 1km.This guide helps further explains grid references.
This is where the compass comes into its own; one side of the compass has a roamer scale (refer back to the Ordnance Survey compass article) that can measure the grid and break it down into 10 chunks which are then accurate to 100m.
Same principle again…along the corridor and up the stairs.
For more advice and training on how to use a map and compass, Jason runs navigation courses that are well worth attending.