Legends of the dashboard: an empirical evaluation of split and joint layout designs for geovisual analytics interfaces

Geodashboards are often designed with explanatory elements guiding users. These elements (e.g. legends or annotations) need to be carefully designed to mitigate split attention or information integration issues. In this paper, we report expert interviews followed by a controlled experiment where we compare two interface designs with a focus on the split attention effect: (1) a multiple-legend layout with explanatory elements located next to each view, and (2) a single-legend layout with all explanatory elements gathered in one place. Different legend layouts did not affect the performance, but affected user satisfaction. 75% of the participants preferred the multiple-legend layout, and rated it with a higher usability score, mainly attributing this preference to the proximity of legend elements to the view of interest. Eye tracking data strongly and clearly verifies that participants indeed make use of the proximity: With the single-legend, the majority of eye-movement transitions were between the single-legend and the closest view to the legend, whereas with multiple-legend participants have shorter and more frequent legend visits, as well as more transitions between legends and views. Taken together, the design lesson we learned from this experiment can be summarized as ‘split the legend elements, but make it close to the explained elements’.