Macs Maps: Orienting your map
Now that you're an expert on map features and grid references, it's time to learn about orienting your map. This means getting your map lined up with reality so you can see which way you want to go. There are two main ways to do this: using a compass, and using land features.
We'll start with the compass method, because once you've got the hang of using it, it tends to be much more effective than using land features.
Firstly, it is important to note that the accuracy of your compass can be affected by magnetic declination. The level of this variation is different throughout the world, so if your adventure relies on specific compass readings, it might be an idea to check out the level of magnetic declination in the area. There are a number of websites which can calculate this for you, such as http://www.magnetic-declination.com/
. Iron and steel objects on the ground or on your person can also distort the compass reading.
The first step is to understand the different parts of the compass. We've highlighted the most crucial features in the diagram below. The direction of travel arrow, highlighted in yellow, points in the direction of your route on the map. The red half of the compass needle, highlighted in green, will point North. The orienting arrow, highlighted here in blue, need to be lined up with the eastings. Eastings, as we learnt about in the map features blog, are the vertical blue lines on your map.
So now we know the main features of the compass. The next step is to orient your map. Make sure you have marked out the route you want to take. Now line up the direction of travel arrow with the first part of your route. Keep the map flat and hold the compass still while the compass needle settles on North. Then rotate the black circle until the orienting arrow and the lines beside it line up with the eastings (vertical blue lines on the map). Now, while holding the map and the compass, rotate your body until the compass needle matches up with the orienting arrow.
To demonstrate this, take a look at the diagram below. Imagine you are beginning your journey at Ludwell Farm Cottages, circled in yellow, and you want to go to Church Farm, circled in red. The route we want to take is marked in blue. Let's go through the process again using this example.
1. Place the compass on the map with the direction of travel arrow following the first section of your route.
2. Turn the black casing until the orienting arrow lines up with the eastings.
3. Holding the compass on the map, rotate your body until the compass needle lines up with the orienting arrow.
As you can see, the direction of travel arrow follows the first section of our route. From this, we can calculate what bearing to begin with. The number on the black circle indicate the degrees from North you need to travel. In this case, we will be travelling in a 20° direction, which is around North-North East.
You can repeat this process at each change in direction to check you're going the right way.
If you don't have a compass, it is possible to orient your map using land features, though this is a much less precise art. This method works only where there are obvious and reliable landmarks, such as hills or rivers. First, place your finger on your current location on the map. Now rotate the map until the land features on the map line up with the land features in reality. Remember this method is not particularly accurate, so it is better to use a compass if possible.
For more info, check out Ordnance Survey's own map reading guide
, or take check out the video below!
Next week we'll learn how to pinpoint your location. Until then, happy mapping!
Learn more about Ordnance Survey's new #GetOutside campaign here