What this lesson teaches
I can read and choose the right maps, graphs, photographs and other visual resources.
Syllabus 8834, Fieldwork, Additional Notes on Data. Students are required to be familiar with the following types of data: Maps: contour maps, choropleth maps, isoline maps, dot maps, flow-line maps, proportional symbols maps and cartograms; Graphs: pie charts, bars, histograms, scatter graphs, radar charts, triangular graphs and line graphs; Photographs: landscape photographs, aerial photographs and satellite images; Others: tables, schematic diagrams, illustrations and cartoons.
Make a guess
You want to show how common a barrier is in each district, where districts have very different populations. Which map fits?
- A flow-line map.
- A contour map.
- A choropleth shaded by the percentage reporting it.
- A choropleth shaded by the total number reporting it.
Show the answer
A choropleth shaded by the percentage reporting it.
A rate removes the effect of population size. Raw totals would make big districts look worse even if the problem is less common there.
Match the map type to what you are measuring, because a rate and a total answer different questions.
A dot map gives each dot a fixed amount. Clusters show concentrations, but dots may not mark exact homes. A choropleth map shades areas by a rate, such as the percentage of people reporting a barrier. Raw totals would mix up population size with how common the problem is.
A proportional-symbol map sizes symbols by area to show totals. Doubling a circle's radius makes its area four times bigger, so check how the key works. A flow-line map shows movement between places, with line width for volume. It may not show the exact route.
Isolines join places with equal values, like temperature. They estimate values between measurement points, so few points mean more uncertainty. Contours are isolines of height.
Every map needs a title, key, source, date, scale and north arrow where relevant. Class boundaries can change how a choropleth looks. Describe patterns, contrasts and exceptions, not just colours.
- Dot map
- Each dot equals a fixed amount.
- Choropleth
- Shades areas by a rate or percentage.
- Flow-line map
- Arrows for direction; width for volume.
Step by step
Name the measure
Count, proportion, flow or continuous value?
Read the key
Amount per dot, class breaks, symbol sizes or line widths.
Describe the pattern
Where, how much, and one limitation.
Worked example: Pick the map for the question
To compare how common it is for homes to lack cooling, use a choropleth of percentages. To estimate demand for help, map the number of those homes with proportional symbols. Keep the same year and totals.
Watch out for this
A darker area always has more people.
A darker shade may mean a higher percentage, even with fewer people.
Check your understanding
Which map best shows the direction and volume of commuting between districts?
- A temperature isoline map.
- A flow-line map with a width key.
- A choropleth of district land area.
Show the answer
A flow-line map with a width key.
Yes. Arrows show direction; width shows volume.