REFEREED PAPER A Methodological Framework for Researching the Usability of the Space-Time Cube Irma Kveladze, Menno-Jan Kraak and Corne´ P.J.M. van Elzakker Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, The Netherlands Email: i.kveladze@utwente.nl In recent years, an increased interest in the use of the Space-Time Cube (STC) to visualize movement data can be witnessed. However, little is known about whether the cube is truly efficient and effective to satisfactorily display complex movement datasets. The limited usability research that has been done did not lead to details on how the STC content should be designed and whether the cartographic design influences the exploration process. The conceptual framework that is proposed in this paper offers an approach to the evaluation of the STC content with special attention for design aspects and the environment in which the STC has to function. Systematic usability studies have to identify the strengths and weaknesses of the STC under different conditions. Therefore, the framework contains phased studies in which real-world data of four use cases of different complexity are used. Keywords: usability, space–time cube, research framework INTRODUCTION The movement datasets accumulated in the last decades are an important source for knowledge discovery and require suitable visual representations for analysis. A wide range of representations as well as interactive techniques have been developed to support the exploration process of complex data. One means of visual representation that requires usability studies is the Space–Time Cube (STC), which has been widely used in different domains for the visualization of spatio- temporal data. Like other visual representations, the STC suffers from overplotting and visual clutter when many trajectories are displayed together. With its increasing use, usability metrics on effectiveness, efficiency and user satisfac- tion become critically important, but only a limited number of usability studies has been executed. This observation forms the motivation for the research framework developed in this paper. First, an overview of STC characteristics is given, followed by a discussion of the literature related to existing STC applications and usability evaluations. A discussion based on a user-centred design approach introduces requirements based on four use cases. In the next section, a visualization strategy is introduced based on cartographic design principles (Bertin, 1983) and Shneiderman’s (1996) information seeking mantra. This is followed by the description of an evaluation setup. VISUALIZATION OF MOVEMENTS Ha¨gerstrand (1970) proposed a framework of time geogra- phy to study social interaction and movement of individuals in space and time. The STC is the visual representation of this framework where the cube’s horizontal plan represents space and the 3D vertical axis represents time. The building blocks of the STC are the space–time path, stations and space–time prism (Lenntorp, 1976; Pred, 1977; Thrift, 1977). The research focuses on the space–time path and stations. The space–time path represents movement through space and time, and shows when and where individuals move and how long they stay at certain places. They have been applied to study gender differences (Kwan, 1999), historical events (Kraak, 2009), movements of national park visitors (Orellana, et al., 2012), etc. Stations refer to the locations where people can meet or stay for some period of time and can be recognized as indication of non-movement activities. Stations were also applied in different applications: earthquakes (Gatalsky et al., 2004), forestry (Andrienko and Andrienko, 2005), archaeology (Huisman et al., 2009), etc. Other methods: The STC has been successfully applied in combination with other methods. Romero et al. (2008) used it for the analysis of people’s movements derived from video streams. Li et al. (2010) used the cube to visually inspect the eye movement data. Demsˇar and Virrantaus (2010) applied the STC to analyze real-time vessel movements. Despite the increasing popularity of the STC, brought about by hard- and software developments and the data rich environment, usability research still remains limited. What has been done is summarized in Figure 1. In most of this research the cube is compared with other graphic representations. The table also lists the user tasks given and the evaluation methods applied. The Cartographic Journal Vol. 50 No. 3 pp. 201–210 International Cartographic Conference 2013, Dresden - Special Issue August 2013 # The British Cartographic Society 2013 DOI: 10.1179/1743277413Y.0000000061