How to select appropriate hue ranges for sequential color schemes on choropleth maps? A quantitative evaluation using map reading experiments

We propose map reading experiments to quantitatively evaluate the selection of hue ranges for sequential color schemes on choropleth maps. In these experiments, 60 sequential color schemes with six base hues and ten hue ranges were employed as experimental color schemes, and a total of 414 college students were invited to complete identification, comparison, and ranking tasks. Both controlled and real-map experiments were performed, each involving a web-based survey and an eye-tracking experiment. In the controlled experiments, the shapes of the map objects were relatively regular, and attribute data were randomized. In contrast, the shapes were complex in real-map experiments, and real data were employed. Our findings show that widely used color schemes with a hue range of 0º yield poor performance in all tasks; 15º hue ranges yield good performance in the comparison and ranking tasks but poor performance in the identification task. For large hue ranges of 120-360º, participants showed good performance in the identification task but poor performance in the comparison and ranking tasks. For 30-60º hue ranges, participants achieved excellent performance in the comparison and ranking tasks and acceptable performance in the identification task. We also found that the ratings of 0-60º ranges were high.

Methods
We recruited 246 college students to participate in the web survey and 23 college students to participate in the eye movement experiment. Through the experiment, we collected their visual data and arranged them according to different visual indicators. Then we process our data through qualitative and quantitative analysis to get the final result.