These lines are drawn using three landmarks you can clearly see from where you stand. The more accurate you will be the better.

Fix your map firmly on a small board so that it doesn’t move (you can use pliers or drawing pins, be careful pins can damage your map). Direct your map precisely, don’t forget the magnetic declination. Leave your compass on the map to check from time to time that you haven’t moved. You then need to find three landmarks around you (a castle, a church, a water tower... Locate them on the map. In the example that follows the three landscapes that we will consider are the church of Mooles, the water tower of Brenchwood and the bridge of Granchy.

With a ruler you will aim at these landmarks. Check out the picture to see how to proceed.

Once you are done, draw the corresponding line on your map.

Once you’ve drawn all three lines your result should look like this :

You can see that these lines cross, making an uncertainty triangle . You are inside that triangle. If you think that your triangle is too big aim at your landmarks once more.