Path Selection

Some of the problems of assuming a least-cost path for boaters to reach their destinations were discussed in section 5.2.3. While some parts of the boating population rely on least-cost paths, others are out to deliberately stretch their trips out as long as possible given their time and fuel resources. For this segment of the population, the static representation of their paths is not an appropriate way to create or summarize their boating activities. Descriptions of these boats in terms of densities and activities per area is sufficient for many management purposes: a more formal mathematical description based on random walks through lattices (Spitzer, 1976) is being developed which would be suitable for evaluating the output of simulations using autonomous agents, but this work is still in a mainly theoretical stage.

Once one has decided that a least-cost path is the best way to represent a boater's selection of how to get from one point to another, there is still the question of what values one uses for parameterization of that step. The values used in table 4.13 were selected as interval variables: they have no real meaning other than that they are non-zero numbers, with some being higher than others. There is no guarantee that the numbers used are the most suitable values for those parameters, and further study would certainly be very useful in finding empirically justified vales for that portion. An informal sensitivity analysis during the design of the model indicated that the actual values of the layers of the cost surfaces were considerably less important than the differences between the layers. Test runs with the values too close together resulted in behaviors such as boats going over land to avoid infringing on the personal space of boats further down a channel, for instance.

One emergent (unplanned) property of the cost surface-based paths was the unusually high percentage of boats that chose to use the ICW and marked channels given the comparatively low advantage of choosing those paths. This property happens to be consistent with observed boater behavior in the bay.