These are maps, where areas are shaded according to a prearranged key, each shading or colour type representing a range of values.
- Choropleths give a good visual impression of change over space.
- Simple technique to use and extremely effective at helping to observe patterns that would otherwise remain hidden in numerical data.
- Spatial anomalies can easily be identified.
- They give a false impression of abrupt change at the boundaries of shaded units. The reality is probably that change is more gradual.
- Variations within map units are hidden.
- You do not know the actual data at any point of the choropleth map.
Let’s look at a past question.
Study Figure 3 which shows rainfall data gathered over a period of 72 hours in November 2009 for part of Britain.
Comment on the usefulness of this technique as a method of displaying this data. (5 marks)
Comment on? On data/stimulus response questions, it means to examine the stimulus material provided and then make statements about the material and its content that are relevant, appropriate and geographical, but not directly evident.
For a mapping technique, your answer must include the strengths and limitations of this technique.