Map Reading and Interpretation
Senior 2 · Geography and Environment
Map Reading and Interpretation
Lesson 4 of 4
18 min
How big is a forest reserve? How much land would a new rice scheme in a valley cover? Land officers, farm cooperatives and environmental officers answer these questions from maps before anyone walks the boundary. Map areas are also a regular examination question because they test whether you really understand scale.
If the feature is a rectangle (for example a planned plot or a plantation block), convert each side to ground distance first, then multiply.
A tea block on a 1:50,000 map is a rectangle 3 cm long and 2 cm wide. Find its area.
Why convert first? If you multiply 3 cm × 2 cm = 6 cm² and then multiply by 0.5, you get 3 km², which is wrong. One square centimetre on this map is 0.5 km × 0.5 km = 0.25 km², not 0.5 km². Converting the sides first avoids this trap.
Most features (lakes, swamps, forests) have irregular shapes. Use the grid squares.
A forest covers 9 full squares and 6 part squares on a 1:50,000 map with 1 km² squares.
Area = 9 + (6 ÷ 2) = 9 + 3 = 12 km² (approximately).
If a map has no grid, trace the outline of the feature onto graph paper (or draw a grid of 1 cm squares on tracing paper), count squares as above, and use the scale to find the area of one square.
Tip
Memory hook. "Sides before squares": change each side to kilometres, then multiply. Area answers are always in square units (km² or hectares; 1 km² = 100 ha), and answers from counting squares are approximate, so say so.
Solution: 4 × 0.5 = 2 km; 3 × 0.5 = 1.5 km. Area = 2 × 1.5 = 3 km².
Solution: 11 + 8 ÷ 2 = 11 + 4 = 15 km².
Solution: 1 cm = 0.25 km, so each side is 0.5 km. Area = 0.25 km² = 0.25 × 100 = 25 ha.
Solution: some part squares are nearly full and others barely touched; treating them all as halves averages out the error but does not remove it.
Summary
Sources and credits
Written by Ganzaa.
