Optimising Yacht Routes Under Uncertainty

The planning of routes for sailing vessels is subject to uncertainty from the weather. This is particularly important in yacht racing where the accuracy of a weather prediction can determine the outcome of a race. With a perfect weather forecast it is possible to use the polar tables of a given yacht to compute a route that minimises its arrival time at its destination. Software that does this for racing yachts is now a standard part of most commercial instrumentation packages. With uncertain weather information the routing problem becomes more difficult. We review two models for optimising yacht routes under uncertainty about the weather. The first of these is suitable for short course racing. It treats the wind as a Markov process, and based on observations of the wind ditrection, it computes tacking and heading decisions at each point of the course so as to minimise the expected arrival time at the next mark. The second model, which is intended for ocean races, models the weather using ensemble forecasts rather than a Markov process. In both models it is possible to represent risk-averse and risk-seeking behaviour.