The use of the Dynamic Voronoi Data Structure in Autonomous Marine Navigation

Marine navigation involves problems not found on land. As well as fixed obstacles, there are objects whose positions change frequently. Apart from surface obstacle avoidance, a boat must contend with bathymetric depth, which is affected by sea floor and tidal changes. Maintenance of a dynamic data structure for automatic pilotage is a complex task. The dynamic Voronoi diagram of points and line segments provides a natural structure for dealing with adjacency-based collision-avoidance problems. Embedding the moving boat within the diagram permits the detection of immediate neighbours within any specified tolerance. Depths may be estimated from neighbouring depth soundings using “area-stealing” techniques, and accommodation made for tidal values at that time. The dynamic structure allows real-time local updating of obstacle and marker positions. Historical log files permit the replaying of past system states. While global navigation goals must be developed by other means, the dynamic Voronoi structure allows for safe local navigation.