This clip demonstrates how to use the scale of a map to calculate distance.
The video
KS3 Geography. Maps and navigation.
Using maps to work out distance.
JOE CROWLEY: Because maps are drawn to scale they’re perfect for working out the exact distance between two features on the landscape. And there’s a number of ways of doing this.
The first thing you need to establish is the scale of the map. The typical maps used by walkers are the Ordnance Survey Explorer maps. These are to the scale of 1:25 000, so every measurement on the ground is exactly 25,000 times larger than on the map.
You’ll find the scale noted on the front of the map, with more details on the bottom of the map itself. An easy and very quick way of gauging distance is to look at how many blue lines your route covers. On a 1:25 000 scale map each of these blue lines - called eastings and northings - are a map equivalent of a kilometre apart. Count how many lines your route covers - and whether it’s in a straight line or not - and you’ll be able to make a rough estimate of the distance you’ll be travelling.
However, you may want to be more precise. If a path is straight, you can measure it simply using a ruler. And on this map one centimetre is 250 metres, therefore four centimetres is a kilometre. And if you want to know how long that is in miles look at the key at the bottom of your map where you’ll find details of how to work out the relevant figure.
But of course, in real life paths are rarely straight. So you can use a piece of string to trace your route…and then simply measure that length.
Download/print a transcript of the video.
Joe Crowley explains that because maps are drawn to scale, they can be used to calculate the exact distance between two points.
Maps have different scales - a popular scale is 1:25,000. Joe points out on a map that this means that every measurement on the ground is exactly 25,000 larger than shown on the map. Each map will tell you its scale on the legend section. On the 1:25,000 series, this means that one centimetre on the map equals 250 metres in the real world.
One way to gauge distance is to look at the blue lines on the map which denote eastings and northings. Each line is 1km apart, so by counting how many lines your route crosses, you can make a rough calculation of distance. But routes are rarely straight, so Joe shows how to calculate length using a piece of string.
This clip is originally from the series Get Lost.
Teacher Notes
Useful when discussing map reading or using maps to navigate.
Students can be asked to discuss the difference between paper maps and digital maps and the significance of map features.
This clip could also help students understand coordinates, contour lines and how map symbols and legends translate to real landscapes.
Encourage students to discuss the importance of observing surroundings and matching them to a position.
Curriculum Notes
This clip will be relevant for teaching Geography.
This topic appears in OCR, Edexcel, AQA, WJEC KS4/GCSE in England and Wales, CCEA GCSE in Northern Ireland and SQA National 4/5 in Scotland
