Tutorials and hands-on lessons for learning

Graduated and Proportional Symbol Maps

Both graduated symbol and proportional symbol maps display the value of data aggregated from a given area using a symbol that is scaled up or down in proportion to the value. Put another way, the bigger the symbol, the larger the value it represents. For proportional symbol maps, the size of the symbols are in direct relation to the value that is being displayed. Graduated symbols use symbol sizes to represent classes of data rather than unique or absolute values. Graduated and proportional symbol maps can be used to represent both raw and standardized (normalized) data. Both graduated and proportional symbols allow users to display trends over multiple data dimensions in one visualization. For example, symbol size could be used to represent a quantity while the symbol color could be used to represent a range.

Graduated point examples
USA Today COVID-19 |NYT Election Results

Map users typically underestimate the difference between symbols sizes, regardless of the symbol type being used. As a general rule, circles are the easiest symbols for users to interpret. Also, visualizing a high density of symbols on a map can be difficult, as symbols may overlap and obscure one another. To remedy this, adjust the opacity of the symbols to enable users to see multiple symbols in the same area.

Examples of data sets appropriate for this map type:

  • Population of the largest cities in the US
  • Location and magnitude of earthquakes

Your turn

Using the concepts that you learned in the choropleth and heatmaps tutorials, use either of the following data sets in Mapbox Studio to create a graduated or proportional symbol map:

Review questions

  1. What is the difference between a graduate symbol and a proportional symbol representation?
  2. What are some drawbacks of using this map type?
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