Bearings
- A bearing is an angle measured clockwise from north. It is always written with three figures, such as 045°, 120° or 300°.
- To measure a bearing, put the centre of your protractor on the starting point and measure clockwise from the north line.
Back bearings
- The bearing of A from B differs from the bearing of B from A by 180°.
- If the bearing is less than 180°, add 180°. If it is more than 180°, subtract 180°. If the bearing of B from A is 070°, the bearing of A from B is 250°.
Scale drawings and maps
- A map scale of 1 : 50 000 means 1 cm on the map is 50 000 cm (500 m) in real life. So 4 cm on the map is 200 000 cm, which is 2 km.
- With a scale of 1 cm to 5 km, 3.5 cm on the map represents 17.5 km.
- To go from real life to the map, divide by the scale.
Using bearings with other maths
- North lines are parallel, so you can use alternate and co-interior angles between them.
- Bearings problems often need Pythagoras or trigonometry too.
Key terms
- Bearing
- An angle measured clockwise from north, written with three figures.
- North line
- A line pointing north, drawn at the point you measure from.
- Clockwise
- In the direction the hands of a clock move.
- Back bearing
- The bearing for the return journey, 180° different.
- Scale
- The ratio between lengths on a drawing or map and real lengths.
- Scale drawing
- An accurate drawing with all lengths reduced or enlarged by the same scale.