Monitoring Orientation of Moving Objects around Focal Points

We consider a setting with numerous location-aware moving objects that communicate with a central server. Assuming a set of focal points of interest, we aim at continuously monitoring object orientations and hence detect situations where many objects get closer to or move away from any such site. Towards this goal, we propose a streaming approach that delegates part of the processing to objects, which relay positional updates upon significant deviations at their course. The central processor maintains the changing distribution of current object headings around each focal point and may issue alerts once it observes many objects moving along a direction (e.g., increased northbound traffic near the stadium). To efficiently answer such navigational queries, we introduce a novel access method that indexes object headings influencing a specific site. Furthermore, we extent this scheme to examine trajectory movements around sites over the recent past. Experimental results verify that this framework is able to cope with scalable numbers of objects at reduced communication cost, while offering instant notification of important trends along diverse directions for multiple focal points.