Scale of a map

Why is this relevant? How is it used?

Every map has a scale, which relates the size of the objects shown on the map to their sizes in real life. The scale enables us to understand how big something is in real life.

For example, if a road is shown on a map, and if 4cm long on the map, the scale lets us understand how long the road is in real life. If the scale of the map was 1 cm = 1 km that means that a line on the map which is 1cm long is showing something which in real life measure 1 kilometre (which is 1,000 metres, or 100,000 centimetres).

If we had that road of 4cm on the map, and the scale was 1 cm = 1 km, then we would know that the road is 4 km long in real life.

Discussion

Scales are usually expressed in the form of two numbers, also called a ratio. For example, where a scale is 1 cm = 1km, that could be expressed as:

1:100,000

This means that anything that measures 1 unit on the map needs to be multiplied by 100,000 to work out how big it is in real life. A scale where 1 cm = 100,000 cm is the same as 1 cm = 1km.

The smaller the second number in the scale (ie 1:12), the larger the items on the map are, and the less that can be seen on the map. These are called large scale maps. These maps will be very detailed, for example a map of a city block, or part of a small country town.

The larger the second number in the scale (ie. 1:500,000), the items are shown as smaller on the map, and more can be seen on the map. These are called small scale maps. These maps are not very detailed, for example, a map of all of the world, or Australia.

An example of small scale and large scale maps is below:

Scale is always shown on a map, and is one of the elements of BOLTSS. Often there is a line shown as the scale, which provides a reference point for measuring distances on the map. The following small scale map has a scale at the top.

Watch a short video explaining scale

Common errors

A common error with scales is thinking that the larger the second number in the scale (ie 1:500,000), then the larger things will appear in the map, and the larger the scale of the map. This happens because it is easy to think larger second number means larger scale.

However, remember that the scale is a ratio or a fraction, and 1/100 is much bigger than 1/500,000. The larger the second number, the larger the denominator of the fraction, and therefore the smaller the scale of the map.

How is this tested or examined?

A multiple choice question can be created which shows two maps of the same area, drawn at different scales. The question then asks which map has the larger scale.