The Basics Of Map Reading With A Compass
15 January 2018
When it comes to hill walking, most of us will have an idea of the most important things to consider when setting out: adequate clothing, food and water, a map, and a mobile phone for emergencies.
However, very few avid hikers actually know how to use a compass which is an extremely useful, and sometimes lifesaving, skill when out climbing mountains.
So, to give you a hand, we’ve put together a post with all the basics you need to know in order to read a map with a compass.
Why do I need a compass?
Firstly, you might be wondering, why do I actually need to use a compass? Isn’t that what GPS on a mobile phone is for? Do people even do that in this day and age?
Well, in answer to your questions, you do in fact need a compass when out walking. Should anything happen to your phone, such as the battery dying or a lack of signal, you would be left without any way of navigating accurately.
Plus, GPS can be difficult to follow when visibility is poor, whilst an accurate compass bearing will keep you on the right track despite thick fog or rain.
Guide to the compass
When it comes to walking, running, or cycling, the baseplate or orienteering compass is the most effective and accurate way of reading a map, so we will be discussing this type of compass in this post.
A baseplate compass is made up of around 8 basic features (although some high tech ones will have more!) which are:
- Base plate: this is the clear plastic base on which the compass is mounted and has multiple lines and scales on it to help you take readings.
- Compass dial: this can be known as the compass housing or compass wheel and is the rotating bezel used to take bearings. The dial will be marked every two degrees to cover the full 360 degrees and will have the four main compass points of N,S,E,W.
- Compass needle: this is the magnetic needle that rotates to find north. The red end will always point to magnetic north whilst the white end will always point to magnetic south.
- Orienting lines: these are lines that are fixed within the compass dial and are aligned to the lines on your map to take your bearing.
- Orienting arrow: this is a fixed arrow within the compass dial and when you take your bearing, you will align the compass needle with this north-facing arrow.
- Index line: this is a line fixed into the compass dial which marks the bearing you want to travel on.
- Direction of travel arrow: this is an extension of the index line to show you which direction of travel you need to take.
- Compass scales: otherwise known as romer scales, these scales help you to measure distance and help you work out your six-figure grid reference.
For a diagram of these features, the Ordnance Survey has created a guide.
Before you begin to take your bearings, it’s important to make sure you’re using the correct north.
If you’re using an Ordnance Survey map, you’ll notice a section called North Points. For the purpose of navigation, you need to use grid north and magnetic north (you can ignore true north!)
How to take a bearing
Step 1: Line up your points
To take a bearing, you need to identify where you are on the map (point A) and where you want to go (point B).
Make sure the map is on a flat surface and line up the edge of your compass with the line between point A and point B, making sure that the direction of travel arrow is pointing towards point B.
Step 2: Align to grid north
Hold the compass still and turn the compass dial so that the ‘N’ magnetic point is facing to the top of the map (i.e. grid north).
When this is done, the orienting lines on the dial should be lined up with the easting lines on the map and the orienting arrow on the dial should be facing to the top of the map.
Step 3: Adjust for magnetic variation
When it comes to accuracy, you need to adjust for the magnetic variation between grid north and magnetic north, which is between 0 to 4 degrees to the west. You can find the adjustment in your map key under ‘magnetic north.’
Once you’ve found the adjustment needed, turn your dial anticlockwise the number of degrees states on the map.
Step 4: Line yourself up
Once you’ve taken the bearing, be careful not to move the compass dial.
Hold the compass flat and near to your body, with the direction of travel arrow pointing straight ahead. Turn yourself and the compass around slowly until the red end of the compass needle lines up with the orienting arrow.
The direction of travel arrow will now be pointing towards point B and where you want to go.
When you’re ready to set off, pick an object in the distance that’s exactly in the right direction and head towards it!
For a guide with added pictures and a video tutorial visit this page.
Now that you’re ready to head out into the great outdoors, this post has three of the best walks in Britain for you to try!