Natasha Pirani, Britta Ricker and Menno-Jan Kraak
The choropleth is a widely used thematic map type. But it is not always ideal to visualize social data in engaging and accurate ways, especially as a standalone map. In this paper we discuss choropleths and two thematic map types with altered geometry: area cartograms and tile maps with repeating icons. To identify benefits and drawbacks of each, we created a choropleth, contiguous cartogram, and repeating icon tile map visualizing the same data from the United Nations Sustainable Development Goal (SDG) indicator about the proportion of women and girls aged 15--49 who have undergone female genital mutilation/cutting in African countries, from SDG 5, on Gender Equality. We conducted a qualitative online survey to collect users evaluations, through informational tasks, quality ratings, and open-ended questions based on interaction with the maps. Results of this preliminary investigation suggest that though users are familiar and therefore more comfortable with choropleth maps, they interpreted thematic map types differently. Specifically, the relative novelty and unfamiliarity of the distorted geometry of cartograms and tile maps may have caused users to engage more thoughtfully with the visualized data and in the cartogram and tile map which are generally considered non-standard thematic maps.