VISIR-I: small vessels – least-time nautical routes using wave forecasts

Abstract

Abstract. A new numerical model for the on-demand computation of optimal ship routes based on sea-state forecasts has been developed. The model, named VISIR (discoVerIng Safe and effIcient Routes) is designed to support decision-makers when planning a marine voyage. The first version of the system, VISIR-I, considers medium and small motor vessels with lengths of up to a few tens of metres and a displacement hull. The model is comprised of three components: a route optimization algorithm, a mechanical model of the ship, and a processor of the environmental fields. The optimization algorithm is based on a graph-search method with time-dependent edge weights. The algorithm is also able to compute a voluntary ship speed reduction. The ship model accounts for calm water and added wave resistance by making use of just the principal particulars of the vessel as input parameters. It also checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. The processor of the environmental fields employs significant wave height, wave spectrum peak period, and wave direction forecast fields as input. The topological issues of coastal navigation (islands, peninsulas, narrow passages) are addressed. Examples of VISIR-I routes in the Mediterranean Sea are provided. The optimal route may be longer in terms of miles sailed and yet it is faster and safer than the geodetic route between the same departure and arrival locations. Time savings up to 2.7 % and route lengthening up to 3.2 % are found for the case studies analysed. However, there is no upper bound for the magnitude of the changes of such route metrics, which especially in case of extreme sea states can be much greater. Route diversions result from the safety constraints and the fact that the algorithm takes into account the full temporal evolution and spatial variability of the environmental fields.

VISIR-I.b: waves and ocean currents for energy efficient navigation

“…where δx is the edge length. The weights δt are then employed for the computation of a time-dependent shortest path, through the same graph search method described in Mannarini et al (2016a) and updated in this manuscript in Sect. 2.4.…”

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VISIR-I.b, the latest development of the ship routing model published in Mannarini et al (2016a), is here presented.The new model version targets large ocean-going vessels by accounting for both waves and ocean currents. In order to effectively use currents in a graph-search method, new equations are derived and validated versus analytical benchmarks.A case study is computed in the Atlantic Ocean, on a route from the Chesapeake Bay to the Mediterranean Sea and vice versa.Ocean analysis fields from data-assimilative models (for both ocean state and hydrodynamics) are employed.

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“…, the latest development of the ship routing model published in Mannarini et al (2016a), is here presented.…”

A new search-and-rescue service in the Mediterranean Sea: a demonstration of the operational capability and an evaluation of its performance using real case scenarios

“…The data concatenation is performed across the time variable. The wind and current data at sea are extrapolated the ocean data towards the coast using a procedure called SeaOverLand (De Dominicis et al, 2013;Mannarini et al, 2016a), which performs an extrapolation of the original data considering for each cell grid point an average of the eight nearest values and then doing different iterations. This procedure optimally fills, for the currents, the gaps that remain between the ocean model domain and the high-resolution coastline.…”

TESSA: design and implementation of a platform for situational sea awareness

“…Projects in this field generally support well-defined scenarios, like oil spill (Zodiatis et al, 2016) or ship routing (Mannarini et al, 2016a). In those cases, stand-alone clients (like mobile apps) or dynamic websites are created and maintained in order to allow the stakeholders to use the service.…”