Two-variable choropleth maps : an investigation of four alternate designs

Halliday, Sandra M. (1987) Two-variable choropleth maps : an investigation of four alternate designs. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (21MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The two-variable choropleth mapping technique is a statistical mapping method that researchers have only seriously considered since the mid-1970’s. The aim of this method is to enable the percipient to distinguish three spatial distributions on a map, i.e. two single geographical distributions and the interrelationship between them. Most of the earliest research questioned the viability of the bivariate choropleth map and found it to be acceptable. Much of the subsequent research was conducted to evaluate its graphic design flexibility to the cartographer and readability to the map user given the intended purpose of the design. This study continues that research trend. Test maps were designed by combining four graphic variables that resulted in the following combinations: value with black pattern, value with white pattern, hue with black pattern and hue with white pattern. A total of four previously untested experimental maps with a 4x4 matrix legend were created and used in conjunction with a task-specific questionnaire to determine the feasibility of the designs. The utility and validity of these designs were analyzed based on the degree to which subjects could interpret correctly the information displayed on each map. One hundred and twenty university students participated in the study. In the experiment black and white patterns were compared in their effectiveness in the map perception process. Both hue and value were similarly compared. Bertin’s three map reading levels were incorporated into the study to measure the level(s) at which the maps were successfully utilized. The majority of the questions were prepared for the intermediate and superior map reading levels since this is where bivariate choropleth maps were designed to excel. Familiarity with the two-variable choropleth map design was another factor examined. The study also examined whether those students more advanced in their academic programs obtained better results. The results strengthened and substantiated the idea that two-variable choropleth mapping is indeed a viable technique for both the cartographer and the map user. No one design was statistically proven to be the most successful overall, since the experimental questionnaire was answered competently by the subjects regardless of the map design they were randomly assigned. The results showed that subjects could answer questions accurately at all three map reading levels. No significant difference in effectiveness was found between black and white patterns nor with hue and value progressions. As the participants worked with and learned how to interpret the required information from the experimental maps, their results improved significantly.

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