We’ve made it to week three in our six-week blog series on map reading skills. Map reading is an essential skill for any explorer or outdoor enthusiast. We’ve teamed up with Steve Backshall to record a series of videos to remind you of the basics and help you feel confident with your map.
- How to read a grid reference, both four-figure and six-figure versions
- Knowing your compass and how to take a compass bearing
- Understanding magnetic north
We’ll share Steve’s video with you, give a summary in the blog and point you in the right direction of further resources and details. Hear what Steve has to say about contour lines:
As Steve said, understanding contours is a key navigation skill as you’ll be able to interpret the landscape of an area just be looking at a map. Contours tell you whether the ground is flat, hilly, undulating, or steep. You can tell whether a route will be a gentle stroll or a hard uphill slog, so you can plan your route more easily.
Contours are shown on Ordnance Survey maps as thin orange or brown lines with numbers on them that show you the height above sea level of any point on the line. The contour lines join points of equal height together. Contour lines very close together indicate a steep slope and contours further apart show a gentle slope.
The vertical interval is the height (elevation) between each contour and they appear 5 or 10 metres apart with thicker lines every 50 metres. The numbers on contour lines are always displayed in ascending height, so if the numbers increase it denotes an uphill slope, and if they decrease it’s a downhill slope.
The relationship between higher and lower contours and the distance between them can give you valuable clues about what the real surface of the ground is like:
Smaller circles show a summit or basin, but the inside of a contour circle is normally higher ground.
Flat areas like river valleys and the sea have very few or no contours.
Contours are only ever on top of one another if it’s a vertical cave or cliff.
A ‘V’ or ‘U’ shape pointing downhill denotes the spur of a hill.
Contours descending in number on either side of a line show a ridge.
Contours bunched together on either side of lower, more evenly spaced contours show a valley or col between two areas of high ground.
Small downward lines inside a contour circle are known as ‘hachure marks’ and signify ground that is sunken beneath sea level.
Using contour lines you can calculate the elevation of your route, or height of travel. This is useful because you can add the uphill distance to the length of your route to get a more accurate estimate of the total distance you’ll go.
Contour lines give you a mental picture of the shape of the ground. Of course, the earth’s surface is rarely, if ever, uniform, so the patterns of contours are often mixed together, which may at first appear confusing.
The best way to get to know about contours is to take a map with you when you’re walking, running or cycling and see if you can spot different landforms and what their contour patterns are. You can match the contour lines on Ordnance Survey maps to what you can see on the ground and practice recognising some of the classic contour shapes.
Happy exploring! I’ll be back next week to talk about how to read a grid reference.