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Map Reading and Interpretation

14 min read

Basic principles of reading maps

A map is a drawing of part of the Earth’s surface, seen from above and reduced to scale. To read a map, look at the title, the key (legend), the scale, the direction (north arrow), the grid (eastings and northings) and the symbols.

Scale

The scale shows how much the map is reduced. It can be stated as a ratio or representative fraction (RF), for example 1 : 50 000, as a statement (1 cm represents 500 m), or as a line scale. At 1 : 50 000, 1 cm on the map is 50 000 cm = 500 m on the ground.

Convert units at the end: 100 000 cm = 1 km.
Worked exampleUsing scale

Two towns are 7.5 cm apart on a map of scale 1 : 50 000. What is the real distance?

  1. Multiply by 50 000.
  2. Change to km.

Answer: The towns are 3.75 km apart.

Relief on topographical maps

Contour lines join points of the same height above sea level. Close lines show a steep slope, lines far apart show a gentle slope, and V-shaped contour lines pointing uphill show a valley. A spot height gives the height of one point, and a trigonometrical station is a surveyed point.

Contour lines and a hillOn the left, a map of a hill with contour lines at 100, 200 and 300 metres. Lines close together show a steep slope and lines far apart a gentle slope. On the right, the cross-section along the line AB shows the same hill from the side, with the steep side where the contours are close.100 m200 m300 mABcross-section A to Bsteepgentle100200300

The gradient of a slope is the vertical interval divided by the horizontal distance.

Use the same units for both. A gradient of 1 : 10 is a slope that rises 1 m for each 10 m.

Statistical maps

Statistical maps show data such as population or rainfall. Dot maps use dots, choropleth maps use colours or shades for different values, proportional symbol maps use circles of different sizes, and flow maps use lines of different widths.

Try itMap scale

Choose the scale (1 : N) and the distance on the map.

Check yourself On a 1 : 100 000 map, 3 cm represents
Check yourself Contour lines close together show
Check yourself A grid reference gives

Key terms

Scale
The ratio between the distance on the map and on the ground.
Contour line
A line joining points of equal height.
Gradient
The steepness of a slope.
Key
The explanation of the symbols used on a map.

Summary

  • Read the title, key, scale, direction and grid first.
  • Ground distance = map distance × scale denominator.
  • Contours show the height and shape of the land.
  • Statistical maps use dots, shading, circles or flow lines.
Earth Systems Photographs in Geography