Minimum Time Sailing Boat Path Algorithm

Abstract

An iterative procedure to solve the nonlinear problem of fastest-path sailing vessel routing in an environment with variable winds and currents is proposed. In the routing of a sailing vessel, the primary control variable is the pointing (heading) of the vessel (assuming that the sails are chosen and trimmed optimally). Sailing vessel routing is highly nonlinear when considering environmental factors, such as winds and currents, and the behavior of the boat, given the weather conditions (i.e., polar diagrams that predict how fast one can sail, given the vessel's pointing relative to the true wind and the wind speed). The key algorithmic contribution of this article is a fastest-path algorithm for graphs with nonconvex edge costs that depend on weather, current, and boat polars. An illustrative scenario, with idealized weather attributes, and a real-world scenario, with parameters generated by numerical weather and current prediction models, are simulated and tested to compare the proposed algorithm against open-source routing software validated by active sailors. Preliminary results from the simulation setups tested are as follows: 1) the proposed sailing boat path algorithm is comparable to the open-source software available; and 2) exploiting the often unused but significant impactor of surface currents and incorporating leeway into sailing boat path planning enables higher fidelity guidance and faster (i.e., shorter time) routes, in comparing against the freely available baseline.

VISIR-2: ship weather routing in Python

“…When considering currents as a factor, the duration of optimal routes could further be reduced by 3.2 %. Additionally, confirming prior work by Sidoti et al (2023), disregarding the role of leeway would lead to an incorrect estimation of the route duration in upwind conditions. Several cases of non-FIFO behaviour were detected, and there is potential for addressing them in the future through the refinement of the current least-time algorithm.…”

“…Furthermore, a sensitivity analysis was conducted, considering both the uncertainty in wind direction and the magnitude of the discretisation step in the numerical solution. Sidoti et al (2023) provided a consistent framework for a dynamic-programming approach for sailboats, considering both leeway and currents. In order to constrain the course of the boat on the available edges on the numerical grid, an iterative scheme was adopted.…”

VISIR-2: ship weather routing in Python

“…Furthermore, a sensitivity analysis was conducted, considering both the uncertainty on wind direction and the magnitude of the discretisation step in the numerical solution. Sidoti et al (2023) provided a consistent framework for a dynamic programming approach for sailboats, considering both leeway and currents. In order to constrain the course of the boat on the available edges on the numerical grid, an iterative scheme was adopted.…”

“…The new ambition is to achieve complete decarbonisation by mid-century, addressing all greenhouse gas (GHG) emissions, with a partial uptake of near-zero GHG technology as early as 2030 (IMO, 2023). While no new measures have been adopted yet, the revised strategy is expected to boost efforts to increase the energy efficiency of shipping in the short term (Smith and Shaw, 2023). In line with the European Green Deal, the European Union has adopted new rules to include various GHG (carbon dioxide, methane, and nitrous oxide) emissions from shipping in its Emissions Trading System (EU-ETS), starting from 2024 * .…”