Evaluating visualization for emergency decision-making under uncertainty

This thesis explores the extent to which the cartographic representation of uncertain geographic information aids or impairs spatial decision-making in the context of emergency hazards, specifically bushfires and floods. Through a series of human subject experiments, utilizing more than 300 subjects and employing a range of increasingly challenging tasks, this research evaluates quantitatively the effects of different map-based representations on spatial decision-making under uncertainty.

These quantitative experiments are amongst the first in cartography and visualization to focus specifically on the task of decision-making under uncertainty, rather than the task of reading levels of uncertainty from the map. To guard against the potential for generosity and risk seeking in decision-making under uncertainty, the experimental design developed is also a pioneer in cartography and visualization in the use of performance-based incentives.

The first series of five experiments explore the impact of five different map-based representations and one text-based representation on the decision to stay or leave a potentially bushfire-impacted home. The initial experiments showed that the choice of representation makes little difference to performance in cases where subjects were allowed the time and focus to consider the decisions. However, with the increasing difficulty of time pressure, and added distractions, there was some variation observed in the results. Under time pressure, subjects performed best using a spectral color hue-based representation, rather than more carefully designed cartographic representations, such as color value and transparency. Text-based and simplified boundary encodings were among the worst performers. To provide contrast to the first three experiments, an experiment without incentives and one that used subjects from the wider community was also conducted and the results compared with the other experiments.

Based upon the results of this first series of experiments, a sixth more complex decision-making routing experiment was conducted with 58 subjects. This final experiment evaluated a further six static methods for representing uncertainty connected to a routing and wayfinding task, associated with a flooding emergency scenario. Under the more complex routing task, it was found that the graphical representation of uncertainty had a significant effect upon the level of risk taken by the participants in choosing their route. In this experiment, subjects performed best when uncertainty was represented using an intuitive "sketchy" based representation. The more cartographically conventional red color hue representation overall exhibited the worst performance.

The results have implications for the performance of decision-making under uncertainty using static maps, especially in the stressful environments surrounding an emergency.