Database Reference
In-Depth Information
(a)
(b)
(c) (d)
Figure 11.3 From raw data to trajectory pattern (Bay of Brest).
an arc between two zones of the graph. Figure
11.3
c,d, illustrating trajectory
patterns, will be presented in Sections
11.2.3
and
11.2.4
.
11.2.2 From Raw Positions to Trajectories
As shown in Figure
11.3
a, the numerous position reports of ships can be put
together in order to build a trajectory and address point-based query limits.
Point-based queries (strictly based on raw positions) exhibit two limits. First, a
computing limit such as point-based spatial queries is very expensive in terms
of computing cost. Second, it reaches a spatial limit as queries are applied
on reported locations provided by the AIS (a ship passing through a narrow
restricted area can report positions on both sides, due to AIS behavior and
