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#279
jeff
Keymaster

Thanks for the positive feedback!

Reducing Distance and Time Resolution will improve accuracy but run slower.

For mid-latitude regions (60N to 60S) there’s little point in reducing Distance Resolution less than 60 NM.

I see people like to go for small time resolutions but I’m pretty happy with a 2 hour value. On the open ocean, winds don’t vary much within that time frame. Near geographic features, or during frontal passages, winds do change rapidly, but GriB forecasts are also less accurate for micro or meso scale phenomena. A useful strategy is to have a look at how the winds are varying over your race. If they are varying a lot, then go for a smaller time resolution.

Reducing Grid Size is the best way to improve accuracy but the time penalty is the square of the inverse of the reduction, which is to say: if you reduce the grid size by a
factor of 2, the running time will increase by a factor of 4. I usually start out with a 60nm grid size and then reduce it if I want to fine tune my route, down to the smallest value I can stand waiting for.

What I say about Max Range is correct. Reducing max range artificially limits the search space, which makes things go faster, but eliminates the (theoretical) possibility of finding the fastest route.

I don’t worry too much about these parameters, because they don’t seem to make much difference in the optimal route. If you find that not to be true, I would be interested to see examples.

  • This reply was modified 2 years, 11 months ago by jeff.