Since maps represent large areas, they cannot be drawn the same size as the real area on the ground. Maps are drawn small in comparison, but they still give us the actual area they cover on the ground and the same distance between places. In order to do this, a map uses a scale. Accurate maps are, therefore, normally drawn to scale. A scale is a relationship between map distance and actual ground distance.
For example 1 centimeter distance measured on the map represents 1 kilometer distance measured on the ground. So when you measure 1 centimeter on the map, the actual distance on the ground represented will be 1 kilometer.
The following are types of map scale representation
- The statement scale; The statement scale is when you make a statement saying what the distance on the map represents on the ground. You may say 1 centimeter measured on the map represents 1 kilometer measured on the ground or 1 centimeter to 1 kilometer. Notice that the statements mention two distances. The smaller distance refers to the map and the larger distance refers to the ground. For the statement scale, the distance on the ground is always given in kilometers or meters. Thus, in this case, the distance of 1 cm on the map represents a distance of 1 kilometer on the ground.
- The Representative Fraction (R. F.); The scale is given as a fraction: 1/10 or as a ratio: 1:10. What it means is that one unit measured on the map stands for ten of the same units on the ground. You can use any units that you are familiar with. So, you can say 1 centimeter represents 10 cm. On most maps, the Representative Fraction is given as a ratio, which is usually 1:50,000 on topographic maps. Note that the larger the Representative Fraction denominator, the smaller the scale and the less detail that can be shown. A scale of 1:25 000 will show more detail than a scale of 1:100000. The smaller the denominator of the Representative Fraction, the larger the scale, and more detail can be shown for a given area.
- The linear scale or line-scale; is the most common scale used for maps and you need to really know how to use it. This is a special ruler that is drawn below a map that can be used to measure an area or distance. It is divided into a number of equal parts. The divisions on the line scale measure map distances and the labeling will give you the distance on the ground. To the right of zero – each scale division represents a distance of 1 kilometer. To the left of zero – the distance representing 1 km is shown.