1. ¹Department of Spatial Information Science and Engineering, University of Maine, Orono, ME, U.S.A.
2. ²School of Marine Sciences, University of Maine, Orono, ME, U.S.A.

Correspondence: Kate Beard, Department of Spatial Information Science and Engineering, University of Maine, Orono, ME 04469, U.S.A. Tel: +1 207 581 2147; Fax: +1 207 581 2206; E-mail: beard@spatial.maine.edu

Received 31 August 2007; Revised 15 November 2007; Accepted 15 November 2007; Published online 20 December 2007.

Abstract

The expanding deployment of sensor systems that capture location, time, and multiple thematic variables is increasing the need for exploratory spatio-temporal data analysis tools. Geographic information systems (GIS) and time series analysis tools support exploration of spatial and temporal patterns respectively and independently, but tools for the exploration of both dimensions within a single system are relatively rare. The contribution of this research is a framework for the visualization and exploration of spatial, temporal, and thematic dimensions of sensor-based data. The unit of analysis is an event, a spatio-temporal data type extracted from sensor data. The conceptual framework suggests an approach for design layout that can be flexibly modified to explore spatial and temporal trends, temporal relationships among events, periodic temporal patterns, the timing of irregularly repeating events, event–event relationships in terms of thematic attributes, and event patterns at different spatial and temporal granularities. Flexible assignment of spatial, temporal, and thematic categories to a set of graphical interface elements that can be easily rearranged provides exploratory power as well as a generalizable design layout structure. The framework is illustrated with events extracted from Gulf of Maine Ocean Observing System data but the approach has broad application to other domains and applications in which time, space, and attributes need to be considered in conjunction.