Map Scale

Once you have decided the objects to be represented, you have to choose the map scale. What is a map scale ? Scale is the amount of reduction that takes place in going from real world dimensions to the new mapped area on the map plane. Technically, the scale of a map is defined as the ratio of distance measured upon it to the actual distances, which they represent on the ground (ICA 1973). In a general way, this numerator will always be a round number (and not 1:25 350). For example, if a straight line on the ground of length 2.5 km is shown on a map by a line of length 2.5 cm, the scale of the map may be calculated from:

Scale calculation

Three terms are frequently used to classify maps according to scale. The scale values attributed to each class is the following: Large-scale maps show small portions of the earth surface; detailed information may therefore be shown. Small-scale maps show large areas, so only limited detail can be carried on the map.

Large scale maps :
Medium scale maps:
Small scale maps:

Scale larger than 1:25 000
1:50 000 to 1:100 000
Scale less than 1:200 000

The following example shows different scales of the same town.
Select a scale by clicking with the mouse the appropriate radio-button.

Map scale example

To have an enlarged version click here (new window)

In the following exercise, you have to determine the correct scale. Choose the answer by clicking the correct checkbox, and submit your answer by clicking the "Submit" button.

Map scale calculation