Operationalizing Trumbo’s Principles of Bivariate Choropleth Map Design

  • Georgianna Strode Florida State University
  • John Derek Morgan University of West Florida
  • Benjamin Thornton Florida State University
  • Victor Mesev Florida State University
  • Evan Rau Florida State University
  • Sean Shortes Florida State University
  • Nathan Johnson Florida State University


Trumbo’s (1981) ideas on bivariate choropleth design have been underexplored and underutilized. He noted that effective map design (including color selection) is directly informed by the intended goal or use of the map (i.e., what questions might the map answer), and he identified three common spatial relationships that can be displayed by a bivariate choropleth map: inverse relationships, a range of one variable within another, and direct relationships. Each is best suited to answering different map readers’ questions. Trumbo also suggested sample color palettes to focus the map reader’s attention on pertinent data. In consultation with Trumbo, we extended his ideas, first by creating focal models that illustrate his three spatial relationships. We then constructed sample maps to examine each of the focal models, and finally compared each model by mapping the same two data sets (of obesity and inactivity). We investigated the visual differences in each of the resulting maps, and asked spatial questions regarding the relationships between obesity and inactivity. Our work validates Trumbo’s ideas on bivariate choropleth map design, and we hope our focal models guide cartographers towards making color choices by linking their map purpose to the appropriate focal model.

Author Biography

Georgianna Strode, Florida State University
Georgianna is an application developer/programmer at the Florida Resources and Environmental Analysis Center (FREAC) of the Florida State University. Her interests include dasymetric population estimation techniques, geovisualization (especially bivariate mapping), and exploring the potential of using the US National Grid (USNG) in a more prominent role within GIS.
How to Cite
Strode, G., Morgan, J. D., Thornton, B., Mesev, V., Rau, E., Shortes, S., & Johnson, N. (2020). Operationalizing Trumbo’s Principles of Bivariate Choropleth Map Design. Cartographic Perspectives, (94), 5-24. https://doi.org/10.14714/CP94.1538
Peer-Reviewed Articles