Most maps are smaller than the ground they represent. Maps have scales to tell us exactly how much smaller they are than the real ground.
A map scale is defined as "the relationship between distance on the map and distance on the ground".
The scale is also an expression of how much the area represented has been reduced in order to fit it onto a map.
A map scale is usually given as a ratio e.g. 1 : 50,000 which you read as "one-to-fifty thousand". This means that every centimeter on the map represents 50,000cm or 500 meters on the ground. This is a large scale map as it gives a lot of detail over a small area of ground.
Other scales include 1 : 100,000 where each centimeter on the map represents 100,000 centimeters or 1,000 meters (1km) of ground.
1 : 15,000 city maps are very useful as they include a lot of detail. Here each 1cm on the map represents only 150m on the ground so a lot of detail can be included in this large scale type of map.
1 : 210,000 maps are useful for planning longer journeys as they are smaller scale maps and include less information but cover a much larger area. Here 1cm is 2.1km on the ground.
Large Scale or Small Scale?
Maps can be described as small scale or large scale.
How do you know which is which?
A handy way is to remember that on a small scale map there is less room and that everything has to be drawn smaller in order to fit. Relatively small features such as streams, small roads and houses have to be left out altogether.
Larger scale maps allow more detail but cover less ground.
As a map maker you need to decide whether you want to cover a large amount of ground with less information included (small scale) or whether you want more information but only about a smaller section of ground (large scale).
Think about it
If you were planning a long road trip, do you think you would use a large or small scale map?
A large scale map would show a lot of information about each small road, river and house position. A small scale map would show a lot of ground but not with every detail included.
You would of course need a small scale map for planning long road trips as it would tell you where the motorways and main roads are to be found.
................................................ ........Map of Cork City
........................................................Copyright Ordnance Survey Ireland
You will find the scale of an Irish Ordnance survey map on the bottom of the map.
In the map shown here the scale is 1:50,000.
This means 1cm on the map = 50,000cm or 500m on the ground. Handy Hint. This is very useful as each grid square side on this map is 2cm. We know that 1cm = half a km, therefore this means that each 2cm square side represents 1 km on the ground as 2 X 500m = 1km.
This makes it very easy to estimate approximately what distance it is from A to B from just looking at the map and the scale.
Click here to find out how to use scale to measure long distances such as the school playground or football pitch.