Map Reading and Interpretation
Senior 2 · Geography and Environment
Map Reading and Interpretation
Lesson 1 of 4
18 min
A rescue team is sent from Musanze to a farm hit by a landslide. The radio message says the farm is "north-west of the health centre". That is useful, but "north-west" covers a wide wedge of hillside. If the message said "bearing 318° from the health centre, 2.4 km", the team could walk almost straight to it. Surveyors, pilots, road engineers and soldiers all give direction in this exact way. In this lesson you learn both methods: compass points and bearings.
A direction tells you which way one place lies from another. The simplest way to give it is with the points of the compass.
On almost every map, north is at the top. If a map has a north arrow, trust the arrow, not the top edge.
A bearing is the angle between the north line and the line joining two places, measured clockwise from north. It is always written with three figures, so 45° is written 045° and 8° is written 008°.
| Compass point | Bearing |
|---|---|
| N | 000° (or 360°) |
| NE | 045° |
| E | 090° |
| SE | 135° |
| S | 180° |
| SW | 225° |
| W | 270° |
| NW | 315° |
On a map, find the bearing of a borehole (B) from a school (S).
If the line SB points into the western half of the map, the angle is more than 180°. A semicircular protractor only reads to 180°, so measure the angle anticlockwise from north and subtract it from 360°. An anticlockwise angle of 42° gives a bearing of 360° − 42° = 318°.
The back bearing is the bearing of the return journey: the bearing of S from B. It always differs by exactly 180°.
Tip
Exam technique. Underline the word from in the question: "the bearing of X from Y" means you stand at Y. Then sketch a rough compass: if your answer says 250° but the place is clearly to the north-east, you measured from the wrong end. Always write three figures and the degree sign.
Solution: SW is halfway between S (180°) and W (270°): (180 + 270) ÷ 2 = 225°.
Solution: ENE is halfway between NE (045°) and E (090°): (45 + 90) ÷ 2 = 067.5°.
Solution: 070° is less than 180°, so add 180°: 250°.
Solution: 300° is more than 180°, so subtract 180°: 120°.
Solution: 360° − 75° = 285°, which is a little north of west (270°), as expected.
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.
