By: Blonde One
Contour lines are the orange lines on an Ordnance Survey Explorer map that tell you height about sea level of the ground. The lines are usually 5 or 10 meters apart and show how steep the hill is according to how close together the lines are.
Before you even start walking contour lines are helpful in planning your route. As you can see from the screenshot, the approach to Brat Tor on West Dartmoor is much more easy going from the East. The nicely spread out contour lines show you that a walk up to Brat Tor from this side would be quite pleasant. The valley in the image of Black Tor is locally known as ‘Killer Valley’! It used to be on the Ten Tors route and teenagers nicknamed it this as they struggled up it with their full packs on their backs. There are two things on this map that tell you which way the hill is going: the river is always going to be at the bottom of a hill, and the line of orange numbers at the top of the image tell you the height about sea level.
The contour lines on the Ben Nevis map are much closer together telling you that this is not going to be a Sunday afternoon stroll!
When you’re out walking the contour lines can help you to work out where you are by matching what you expect to see, in terms of hills and valleys, with what you can actually see.
Copyright Ordnance Survey 2020