Triangulation is a way of using the compass and map to fix your position. There will be times when you are not sure of your exact position, or indeed when you are completely and utterly lost! If you a map of the local area and you can see some prominent features then you can use the map and compass together to pin down where you are.
You must first make sure you can identify several landmarks (at least 3 to on the safe side) both in real life and on the map. If you were to set up the map then you will find this task a little easier. Try to find landmarks that are evenly spaced. For example if you can see 3 prominent features try to pick ones that are about 120° apart. This will cut down on errors.
- Locate 3 prominent features approx. 120° apart
- Work out the bearing of one of the features
- Find the feature on the map
- Place the compass on the map so that the edge of the compass points towards the feature
- Rotate the entire compass until the meridian orienteering lines (the faint blue lines marked on the dial itself) are aligned with north on the map (e.g. a vertical blue grid line on the map). Note: This method has NOT taken magnetic variation into account and this may produce a serious error depending upon your position on the Earth
- Draw a line from the feature back towards your position (you should be on this line somewhere)
- Now repeat all of the above for the other landmarks
- Your approximate position should be where the lines intersect. In practice if you have taken 3 readings then the lines will produce a triangle ( in theory they should intersect but this rarely happens in practice!). Your position is somewhere within the triangle (hence why the process is called triangulation)
If you know your position to be on a easy to recognise feature (e.g. you are standing on top of a hill, in a stream or better still in a pub) then only one or two bearings should be needed. Simply look at where your line crosses the hill crest, stream or bar.
Be sure to check out the excellent resources provided by Graham from the 12th Andover West. The micro navigation resources are work of the highest quality and an incredibly useful tool to help those who are teaching bearings