17 September 2015

Model description

VISIR, “discoVerIng Safe and effIcient Routes”, is a model for the computation of optimal nautical routes. In VISIR-I, the first version of the system, the optimization considers the sailing time, while the navigational safety is treated as a constraint.

VISIR-I considers medium and small motor vessels with a displacement hull. The model consists of three components: a processor of environmental fields, a ship model, and an optimization algorithm.  The ship model in VISIR-I accounts for calm water and added wave resistance, making use of vessel principal particulars. Furthermore, the systems checks the optimal route for parametric roll, pure loss of stability, and surfriding/broaching-to hazard conditions. The optimization algorithm is based on a graph search method with time-dependent edge weights. The algorithm is also able to suggest a voluntary ship speed reduction.

VISIR-I is coded in Matlab®.

 

Input 
VISIR-I employs significant wave height, wave spectrum peak period, and wave direction forecast fields from an implementation of the WaveWatch-III model in the Mediterranean Sea.

Output 
For each execution, VISIR-I computes two types of routes: geodetic and optimal. The geodetic route is the straightest path between departure and arrival location given the coast topology and the bathymetry, without taking into account the sea-state. The optimal route is a geodetic route that also takes into account the sea-state and, if flagged a few vessel stability constraints.  

Flow chart of the code of VISIR-I model.
Screen Shot 2015-12-02 at 17.12.01
VISIR-I graph structure.

Screen Shot 2015-12-02 at 17.12.26

 

Some Output Example

 Examples of VISIR routes (black: geodetic, red: optimal)


Example of VISIR along-route information: timeseries of Speed Over Ground (SOG):

Screen Shot 2015-12-02 at 17.13.58

 

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