Helical time representation to visualize return-periods of spatio-temporal events

Numerous methods have been developed to integrate temporal dimension in geovisualization environments. However, the return-period of cyclic spatio-temporal events is still difficult to visualize in most time visualization tools used in geovisualization, like timelines or timewheels. However, some temporal diagrams, which combine linear and cyclic aspects of time, allow the visualization of the return-period of these events. These diagrams represent time by a chronological succession of instances of a considered period. If this period and the events return-period are equal, the return-period can be highlighted. Among these diagrams the time coil diagram proposed by Edsall and Peuquet represents time with a helix. These diagrams are interactive and the represented period value can be modified to visualize the return-period of different cyclic events. However, the values set to the period represented by the diagram are generally limited to usual periodic scales like hours, days, weeks, or months. In this paper we propose a new geovisualization tool, based on the time coil diagram that allows user to dynamically set any value of the represented period in the helical diagram. This new visualization tool enables both to explore data and to find possible new cyclic events types as well as illustrating the return-period of any cyclic event type.