These methods can all help you to locate your position when you cannot be sure where you are. Using a resection to triangulate your position on a map Inside the triangle is your approximate current location. You should now have three lines drawn on your map, creating a small triangle where they cross one another.
Repeat the steps you took to obtain a single back bearing for all three features you can see. It is possible to use just two features, but this will severely affect the accuracy of your pinpointing. The three features should be spread out, ideally with 120º between each (for example, one in front of you, one if you look over your right shoulder and the other over your left shoulder). If there are no man-made features use natural features such as the crests of hills, but be careful with trees and water, as these can change size and shape over time, making it easy to mis-identify them. You need to begin by taking the bearings of three features in sight, which are also on your map. TriangulationĪ resection is similar to a back bearing, but can be used if you are in the middle of open countryside or on an unknown track. Where the line crosses the track you are on is your approximate current location. If possible, draw a line along the base plate. Now carefully slide the compass across the map so one of the edges of the base plate crosses the feature you spotted on the landscape on the map. Line the orienting lines up with the eastings (the grid lines running north–south) on your map. The magnetic variation is currently 0º to 5º throughout Great Britain (this amount changes annually, so check your OS map to work out the most current value). You need to deduct magnetic variation from the compass reading to convert it. This bearing is a magnetic bearing rather than a grid bearing, which your map uses. With the direction of travel arrow pointing at the feature, turn the compass housing so the orienting line sits under the red half of the compass needle.įinding your location using a compass bearing Looking at your compass, detect the direction the feature is from your current location. If you are on a known track with an identifiable feature in sight (which also appears on your map) you can take a bearing in the direction of the feature and use it to calculate your location. Using several transit lines to pinpoint your location Pinpointing your location with a compassĪn alternative to using transit lines and relying on sight is to use a compass to locate your position. By drawing lines on a map, extending the existing lines of linear features, you can create several transit lines that will help you pinpoint your location (as shown below). It’s also possible to create transit lines using linear features such as walls, fences or straight streams, even if the features won’t line up as they did above.
When you see the two features on the landscape line up as you walk along the track, you’ll be at the point where the line on your map crosses the track (as shown here). As you walk along a track (which appears on the map) there will only be a single point where two features appear in a direct line with each other.ĭraw a line on the map that crosses through both features and continues across the track you’re walking on. When you know two or more features on a map will line up with one another along your journey you can form a transit line.
Some methods will rely on your eyesight while others use your compass. These techniques can be used very effectively once you’ve learned to interpret the features of a map.
Here are several techniques to help pinpoint your location on a map. it's also a also critical skill in an emergency, where giving an accurate grid reference to rescue teams is vital. Pinpointing your location is useful to make sure you’re moving in the right direction or can help you to locate your position on the map if you are lost.
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