1. Choropleth maps
Used to demonstrate trends in data

2. Choropleth maps
A choropleth map provides an easy way to visualise how a measurement varies across a geographic area.
Choropleth maps use graded differences in shading or colour in order to indicate the values of a property. The darkest colour shows the highest value, through to the lightest colour which shows the lowest value.

3. Choropleth map of urban population (%)
The lightest colour shows the lowest % of the population urban
The darkest colour shows the highest % of the population urban
Various shades of the same colour are used to show value.
A legend is used where data is grouped with regular intervals between each group
Data sourced from: The World Bank: Urban population (% of total)

4. Creating choropleth maps
There are six steps involved in creating a choropleth map.
Step 1 — look at the data
Step 2 — rearrange the data
Step 3 — determine breaks
Step 4 — choose colour scale
Step 5 — shade the map
Step 6 — finish the map (BOLTSS)

5. Step 1 Look at the data table.
What is the data we want to represent on the map?
What is the unit of measurement?
What are the highest and lowest values and what is the difference between them?
Table 1: Average rainfall for Australian states and territories from 1961–1990
State/Territory
Average rainfall 1961–1990 (mm)
New South Wales and ACT
566
Northern Territory
548
Queensland
630
South Australia
236
Tasmania
1168
Victoria
654
Western Australia
352
932
Source: Australian Bureau of Meteorology

6. Step 2 Rearrange the data from the highest value to the lowest value.
Table 1: Average rainfall for Australian states and territories from 1961–1990
State / Territory
Average rainfall 1961–1990 (mm)
Tasmania
1168
Victoria
654
Queensland
630
New South Wales and ACT
566
Northern Territory
548
Western Australia
352
South Australia
236
highest value
lowest value
Source: Australian Bureau of Meteorology

7. Step 3
Use your rearranged data to work out ‘logical’ breaks to create the required number of data sets (usually between four and six). There must be continuity in the values (that is, no gaps in the numbers). You may use < (less than) and > (greater than).
Table 1: Average rainfall for Australian states and territories from 1961–1990
State/Territory
Average rainfall 1961–1990 (mm)
Tasmania
1168
Victoria
654
Queensland
630
New South Wales and ACT
566
Northern Territory
548
Western Australia
352
South Australia
236
900+
600–899
300–599
<300
Source: Australian Bureau of Meteorology

8. Step 4 Choose a colour scale for your legend. For example:
Table 1: Average rainfall for Australian states and territories from 1961–1990
State/Territory
Average rainfall 1961–1990 (mm)
Tasmania
1168
Victoria
654
Queensland
630
New South Wales and ACT
566
Northern Territory
548
Western Australia
352
South Australia
236
900+
600–899
900+
600–899
300–599
<300
300–599
<300
Source: Australian Bureau of Meteorology
Lightest colour and lowest value is located lowest!

9. Step 5
Shade the map.

10. Step 6
Complete the map, ensuring all map components are included (BOLTSS).
900+
600–899
300–599
<300
Average rainfall for Australian states and territories from 1961–1990
Average rainfall (mm) N
Scale: Unknown
Source: Australian Bureau of Meteorology

11. References
Background slide: Modified from: CIA,
Slides 5—8 Data sourced from: Bureau of Meteorology data cited in Rainfall distribution (National Water Commission) n/index.aspx?Menu=Level1_3_1_2