RoseTrajVis: Visual Analytics of Trajectories with Rose Diagrams

In this paper we propose RoseTrajVis, a visual analytics system for studying trajectories using rose diagrams, inspired in a classic visualization technique for aggregating data. The rose diagram is composed of sectors (petals) that aggregate trajectories given their direction and show their speeds within an area around a point in a map. It also includes colored arrows on the border that point to the origin and destination of the trajectories and show their average speed. RoseTrajVis enables users to place rose diagrams over a map view and interact with them by applying time, speed and distance to origin/destination filters, and by adjusting the aggregation radius, allowing the visualization of commuting patterns in a city. We prepared a prototype of RoseTrajVis with taxi data, and evaluated the completion times and errors of users carrying out trajectory analysis tasks, and also collected feedback from a domain expert. Results revealed that completion times varied with task complexity, being longer for tasks requiring exploratory analysis of the trajectories on a map, and that almost no errors were made by users. The expert mentioned that RoseTrajVis provides an innovative way of analysing aggregate trajectories and has the potential to be useful in several professional areas.