📍 4 figure reference
Gives a whole grid square. Take the easting on the left of the square, then the northing on the bottom of the square. The two lines meet at the bottom-left corner of the square.
Cartographic Skills » Grid References, Directions and Distance
What you'll learn this session
Study time: 30 minutes
Cambridge spec: Geographical skills, Cartographic skills
- How to read a map using its key, symbols and scale
- How to give 4 and 6 figure grid references, and latitude and longitude
- How to give directions with the 16-point compass and bearings
- How to measure distance and estimate area on a map
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Unlock This CourseReading a map: key, symbols and scale
A map is a drawing of a place from above. Before you answer any map question, look at three things: the key, the symbols and the scale.
Key terms:
- Symbol: a small picture, colour or line that stands for a real feature, such as a blue line for a river.
- Key: the box that explains what each symbol means.
- Scale: the link between a distance on the map and the real distance on the ground.
Scale is often shown as a ratio. On a 1:50 000 map, 1 cm on the map is 50 000 cm on the ground, which is 500 m. On a 1:25 000 map, 1 cm is 25 000 cm, which is 250 m. A 1:25 000 map shows more detail, but a smaller area.
| Scale | 1 cm on the map is | Grid square on the map |
|---|---|---|
| 1:50 000 | 500 m on the ground | 2 cm, so 1 km |
| 1:25 000 | 250 m on the ground | 4 cm, so 1 km |
Grid references
Maps are covered in a grid of squares. The vertical lines are called eastings and the horizontal lines are northings. Each line has a number. These numbers let you give the exact position of any place.
Along the corridor, then up the stairs
Read the easting (across) first, then the northing (up). Eastings before northings, every time.
🎯 6 figure reference
Gives a point inside the square. Imagine the square cut into tenths both ways. Add the tenths across to the easting, then the tenths up to the northing.
Worked example
On a made-up map of Ashby Vale, a church sits in the grid square with easting 34 and northing 71. It is 3 tenths across the square and 8 tenths up.
4 figure reference: easting 34, northing 71, so 3471.
6 figure reference: easting 34 and 3 tenths is 343. Northing 71 and 8 tenths is 718. So 343718.
To go backwards, split a 6 figure reference into halves. For 351726, the easting is 35 and 1 tenth, and the northing is 72 and 6 tenths. The square is 3572.
Co-ordinates, latitude and longitude
Co-ordinates are pairs of numbers that give a position. Grid references are one type. For the whole world we use latitude and longitude. You met latitude in the tropical rainforest lesson; here you use it to give a position.
Key terms:
- Co-ordinates: a pair of numbers or letters that fix a position on a map.
- Longitude: the angle east or west of the Prime Meridian (0 degrees longitude), from 0 to 180 degrees.
Latitude is the angle north or south of the Equator (0 degrees), from 0 to 90 degrees. Give latitude first, then longitude, with N, S, E or W. Cape Town in South Africa is at about 34°S, 18°E: 34 degrees south of the Equator and 18 degrees east of the Prime Meridian.
Directions: the 16-point compass and bearings
The 16-point compass gives the four main points (N, E, S, W), the four in between (NE, SE, SW, NW) and eight more such as NNE (north-north-east) and WSW (west-south-west). Between each pair of neighbouring points is 22.5 degrees. Give the direction from one place to another: "the school is NNE of the bridge" means you travel from the bridge towards NNE.
A bearing is more exact. It is an angle measured clockwise from grid north and written with three figures.
| Direction | Bearing |
|---|---|
| North | 000° |
| North-east | 045° |
| East | 090° |
| South | 180° |
| West | 270° |
| North-west | 315° |
Key terms:
- Grid north: the direction of the vertical grid lines on the map. It is the zero line for bearings.
- Bearing: a direction given as an angle from grid north, measured clockwise.
How to measure a bearing
- Draw a straight line between the two places.
- Put the centre of the protractor on the starting place, with 0 on the grid north line.
- Read the angle clockwise to your line and write it with three figures, for example 047°.
Measuring distance
Straight line: measure with a ruler, then use the scale. Worked example: two bridges are 4.6 cm apart on a 1:50 000 map. Each centimetre is 0.5 km, so 4.6 × 0.5 = 2.3 km.
Curved line, such as a road or river:
- Put the edge of a sheet of paper along the start of the road and make a pencil mark.
- Turn the paper at each bend, keeping the edge on the road, and make a new mark.
- When you reach the end, lay the paper against the scale line and read off the distance.
Worked example: the paper edge shows a winding road is 9.2 cm long on a 1:25 000 map. Each centimetre is 0.25 km, so 9.2 × 0.25 = 2.3 km.
Estimating area
Each grid square on these maps is 1 km × 1 km, so it is 1 km2. To estimate the area of a lake, count the whole squares. Count a part square as one if it is more than half full, and ignore it if it is less than half. Worked example: a lake covers 8 whole squares, 5 squares more than half full and 6 squares less than half full. Estimate: 8 + 5 = about 13 km2. It is only an estimate, because the edges of the lake are not straight.
Common mistakes
Common mistakes
- Writing the northing first. Remember: along the corridor, then up the stairs.
- Using the line on the right or the top of the square. Always use the bottom-left corner.
- Measuring a bearing from the nearest compass point instead of grid north, or going anticlockwise.
- Forgetting to convert: 1 cm is 0.5 km on 1:50 000, not 1 km.
- Measuring a curved road with a straight ruler line.
Exam-style question
Fig. 1.1 is a made-up 1:25 000 map of Ashby Vale. The bridge is at 482631 and the station is 6.4 cm from the bridge in a straight line. The campsite is due west of the bridge, and a footpath runs north-east from the bridge to the station.
(a) Give the 4 figure grid reference of the square that contains the bridge. [1]
(b) Calculate the real distance from the bridge to the station in kilometres. [2]
(c) State the bearing of the campsite from the bridge. [1]
(d) Describe how you would measure the length of a winding road on the map. [3]
(e) Explain how grid references, scale and bearings can be used together to plan a walk from the bridge to the campsite. [6]
Model answer
(a) 4863 (1)
(b) 1 cm is 250 m, or 0.25 km (1). 6.4 × 0.25 = 1.6 km (1).
(c) 270° (1)
(d) Place the edge of a sheet of paper on the start of the road and mark it (1). Turn the paper at each bend, making a mark each time (1). Lay the paper against the scale line and read off the distance (1).
(e) Level 3 (5-6 marks): A 6 figure grid reference such as 482631 gives the exact position of the bridge, so the walker knows where to start, and the campsite can be located in the same way. The direction can be given as a bearing, measured clockwise from grid north with a protractor, which is 270° for the campsite from the bridge, so the walker can follow it with a compass. The scale is then used to find the distance, because each centimetre on a 1:25 000 map is 250 m, so the walker can work out how long the walk will take. The grid references show where to go, the bearings show which way to go and the scale shows how far, so together they give a complete plan for the walk.
Exam tip
In a calculation, show the scale conversion (1 cm = 250 m) as your first step, so you can still earn a mark if the final arithmetic goes wrong.