A methodology for conducting a study into the communicative effectiveness between choropleth maps and cartograms

In recent years, both cartograms and choropleth maps have grown in popularity as a chosen method of communicating spatial data, often in the context of an infographic. However, little is known about the effectiveness of these types of maps as a communicative tool. This report is an empirical study designed to firstly identify what method of visualisation is more effective in communicating spatial data between two types of map; and secondly, establish any rules associated with the type of data to be visualised, that those communicating spatial data must consider when choosing the type of map to use. Following the controlled test, significant findings were recorded, showing a clear difference in communicative effectiveness between the two map types. Regardless of the participant’s personal preference, our research shows that the area cartogram is the most effective method of communicating a simple message, whereas choropleth maps are more successful at simultaneously communicating opposing values. This report describes the methodology behind a trial that was designed to measure the communicative effectiveness between two common formats of data visualisation. The first part of the report introduces the background behind this area of research, followed by the methodology employed to help identify the strengths and any weaknesses in their communicative power. The results obtained from this research have propelled our understanding of communicative effectiveness beyond any work previously published; establishing guidelines on how and when such visualisations should be used, along with controversial findings showing the preferred choropleth map to be less effective than the cartogram.