Map Reading and Interpretation
Senior 2 · Geography and Environment
Map Reading and Interpretation
Lesson 3 of 4
20 min
A district plans to build a feeder road to a new health centre. Before any money is spent, a planner measures the route on a map to estimate its length and cost. Walkers, moto drivers and lorry companies do the same thing when they plan a trip. To turn a length on paper into a length on the ground you need the map's scale.
The scale of a map is the ratio between a distance on the map and the same distance on the ground. It can be shown in three ways:
Convert 1:50,000 into a statement scale in kilometres.
A quick rule: to change "1 cm represents X cm" into kilometres, divide X by 100,000.
On a 1:50,000 map, the straight line between two schools measures 7.4 cm. How far apart are they on the ground?
7.4 cm × 0.5 km per cm = 3.7 km.
Roads and rivers bend, so a ruler alone will not do. Two methods work:
A road measured with a thread is 12.6 cm long on a 1:25,000 map. On this map 1 cm represents 25,000 cm = 250 m = 0.25 km. So 12.6 × 0.25 = 3.15 km.
Always give the answer in the units the question asks for, usually kilometres, and state that curved measurements are approximate.
Tip
Exam technique. Write the scale conversion as your first line of working (e.g. "1:50,000, so 1 cm = 0.5 km"). If you make a slip later, the examiner can still award the method mark. Large scale (1:10,000) shows a small area in great detail; small scale (1:1,000,000) shows a large area with little detail.
Solution: 1 cm = 25,000 cm = 25,000 ÷ 100 = 250 m.
Solution: 6.8 × 0.5 = 3.4 km.
Solution: 1 cm = 20,000 cm = 0.2 km. 14.5 × 0.2 = 2.9 km.
Solution: 9 × 0.5 = 4.5 km. Time = distance ÷ speed = 4.5 ÷ 4.5 = 1 hour.
Summary
Sources and credits
The worked examples and practice items are written by Ganzaa.
This lesson adapts CC BY-SA material and is shared under CC BY-SA 4.0.
