Towards a Ship Routing Decision Support System for an Operational

In the framework of TESSA1 and IONIO2 projects, a ship routing Decision Support System (DSS) is being developed. The DSS is aimed to compute optimized ship routes in the Mediterranean Sea, taking into account constraints for navigational safety. The DSS will make use of operational oceanographic as well as meteorological forecast fields and will provide free online access to the service. The System is based on a graph-theory approach, where graph nodes represent possible ship positions and graph edge weights are the times necessary for the ship to traverse the internodal distance. Such traversal times depend on environmental forcing fields (wave height, wave period, wave direction, surface current, Stokes ’ drift). Since ship routes may last several hours or even days, the temporal evolution of the forcing fields during the route cannot be neglected. The route leading to minimum possible total navigation time is searched for. Thus, the problem has the mathematical form of a Time-Dependent Shortest Path (TDSP) problem. Under proper assumptions [1], TDSP can be solved using e.g. a modified version of Dijkstra’s algorithm [2], which takes into account the temporal dimension. In addition to this, the DSS prototype takes into account the fact that certain combinations of values of environmental forcing fields and ship structural and dynamical parameters may lead to dangerous motions [3]. Our approach is to remove from the graph those edges corresponding to such unsafe situation. Thi