Cartographic Skills – Week 7 – Choropleth & Proportional Symbols

GIS 3015: Cartographic Skills

Week 7 Lab: Choropleth & Proportional Symbols

The Choropleth maps below apply the concepts of graduated and proportional symbol mapping to depict Europe’s population density, wine consumption, and percentages of female and male population.  

The maps also reflect the testing of different data classification methods to select the method that maps the data in the most accurate fashion.  For example, the top map uses the Quantile method to represent population density and the Natural Break method to represent wine consumption.  The bottom maps use the Quantile method to represent the percentages of female and male population.

Below are some of the steps in ArcGIS to use proportional and graduated symbols:

Proportional and graduated symbols can be found under the Layer > Properties > Symbology tab. 

Proportional symbols are found on the left panel (Show) under Quantities.  A value under the drop down menu in Fields must be selected and a normalization selection may be necessary, though in our case the wine consumption data was already normalized as liters per capita.  Under the Symbol section, it is important to make the Background color hollow and to select the symbol, color, and minimum size under Minimum Value.  The number of symbols to be displayed in the legend must also be selected on this screen.

Graduated symbols are found on the left panel (Show) under Quantities.  A value under the drop down menu in Fields must be selected and a normalization selection may be necessary, though in our case the wine consumption data was already normalized as liters per capita.  Minimum and maximum symbol sizes must be selected for proper representation.  A data classification must be selected under the Classification section with various options available including the number of classes.  In my case, I found Natural Break to provide the best representation of this data with graduated symbols.  The labels can be formatted by right-clicking on any label and selecting Format Label - I reduced the number of decimal to save space on the legend.  The Range can also be cleaned up here for rounding and easy reading.