Embedding Temporal Display into Maps for Occlusion-Free Visualization of Spatio-temporal Data

It is often necessary to analyze spatio-temporal data such as traffic flow, air pollution, and vehicle trajectories in a city. A map is often used to show the spatial context while various temporal displays like time series plots can be used to present the changes in the data over time. In this paper, we present a novel visualization that can seamlessly embed temporal displays into a map for occlusion-free visualization of both the spatial and temporal attributes of the data. We first extend the seam carving algorithm to broaden the roads of interest in a map with the least distortion to other areas, and then embed temporal displays into the roads to reveal temporal patterns without the occlusion of map information. We study various design choices in our method, including the encoding of the time direction and temporal display, and conduct two comprehensive user studies to validate our design decisions. We also demonstrate the usability of our approach with case studies on real traffic flow data in a major city.