Computing the Cardinal Direction Development between Moving Points in Spatio-temporal Databases
In the same way as moving objects can change their location over time, the spatial relationships between them can change over time. An important class of spatial relationships are cardinal directions like north and southeast. In spatial databases and GIS, they characterize the relative directional position between static objects in space and are frequently used as selection and join criteria in spatial queries. Transferred to a spatiotemporal context, the simultaneous location change of different moving objects can imply a temporal evolution of their directional relationships, called development. In this paper, we provide an algorithmic solution for determining such a temporal development of cardinal directions between two moving points. Based on the slice representation of moving points, our solution consists of three phases, the time-synchronized interval refinement phase for synchronizing the time intervals of two moving points, the slice unit direction evaluation phase for computing the cardinal directions between two slice units that are defined in the same time interval from both moving points, and finally the direction composition phase for composing the cardinal directions computed from each slice unit pair. Finally, we show the integration of spatio-temporal cardinal directions into spatio-temporal queries as spatio-temporal directional predicates, and present a case study on the hurricane data.
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