Modeling and Visualizing Regular Human Mobility Patterns with Uncertainty: An Example Using Twitter Data

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Traditional space-time paths show the spatiotemporal trajectories of individuals in one to several days. Based on data for such short periods, these space-time paths may not be able to show regular activity patterns, which are pertinent to various types of planning and policy analysis. Travel data gathered for longer periods may capture regular activity patterns, but footprints captured by these data also include irregular activities, introducing noises or uncertainty. Our objective is to determine the representative spatiotemporal trajectories of individuals, accounting for stochastic disturbances and spatiotemporal variability, but using activity data with longer duration. Therefore, we explore using Twitter data which have relatively low and irregular spatial and temporal resolutions. This article introduces a methodology to construct individual representative space-time paths using various aggregation and spatiotemporal clustering techniques. To depict and visualize spatiotemporal trajectories with uncertain information, we propose "space-time cones" of variable sizes to reflect the spatial precision of the paths and use colors on the cones to represent the confidence level. To illustrate the proposed methodology, we use the geo-tagged tweets for an extended period. Our analysis indicates that the representative space-time path reasonably describes an individual’s regular activity patterns. As visual elements, cones and cone colors effectively show the varying geographical precision along the path and changing certainty levels across different path segments, respectively.