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Graph-Search and Differential Equations for Time-Optimal Vessel Route Planning in Dynamic Ocean Waves

Mannarini, G., D.N. Subramani, P.F.J. Lermusiaux, and N. Pinardi, 2019. Graph-Search and Differential Equations for Time-Optimal Vessel Route Planning in Dynamic Ocean Waves, IEEE Transactions on Intelligent Transportation Systems, sub-judice.

Time-optimal routes planned by VISIR, a graph-search-based marine vessel route planning system, are evaluated and compared to the numerical solution of the fundamental differential equations governing time-optimal reachability and paths in dynamic environments. The comparison exercise employs identical setups: topological constraints, dynamic wave environmental conditions, and vessel-ocean parametrizations, while advection by external currents is neglected. The emphasis is on predicting the time-optimal ship headings and Speeds Through Water (STW) constrained by dynamic ocean wave fields. Some VISIR upgrades regarding angular resolution, time-interpolation, and static navigational safety constraints are introduced. For the time-optimal path planning of a vessel whose STW is constrained by realistic dynamic waves but whose motion is not advected by strong external flows, the deviations of the graph-search results relative to the solution of the exact differential equations in both the path duration and length are found to be of the order of the discretization errors, and the solutions converge for sufficient resolution.