Fig. 2

Illustration of ORTEGA for identifying potential interaction between two moving entities (modified from [9]). Yellow-filled ellipses represent intersecting PPAs where potential interaction can occur. For each pair of intersecting PPAs, the following condition should be met, \([t_i^{e_1}-\tau ,t_{i+1}^{e_1}+\tau ] \cap [t_j^{e_2},t_{j+1}^{e_2}] \ne \phi\) or \([t_i^{e_1},t_{i+1}^{e_1}] \cap [t_j^{e_2}-\tau ,t_{j+1}^{e_2}+\tau ] \ne \phi\), where \(t_i^{e_1}, t_{i+1}^{e_1}, t_j^{e_2},t_{j+1}^{e_2}\) are the times when moving entities visit the corresponding GPS location. The two green dashed rectangles highlight two continuous interaction segments. The interaction duration can be computed by taking the difference between a continuous interaction segment’s start and end times. In Segment 1 of continuous interaction, the duration (x) exceeds the threshold value (\(\delta _t\)), classifying it as a concurrent interaction. In contrast, Segment 2, with a duration (y) shorter than \(\delta _t\), is categorized as an encounter