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6/14/2022 7:37 am  #1


Extend current in time

Folks, it is my understanding that this feature will extend the last GRIB current vector indefinitely until the calculated route completes. 

I have two versions of a current GRIB.  The first is for a single point in time. The second repeats the same info for 7 days.

Each produces a different Optimize result. The single point GRIB is clearly missing current features incorporated by the week long GRIB.  Extend Current in Time is enabled.

Any insights?

Cheers
 

Last edited by WoobaGooba (6/14/2022 6:59 pm)

 

6/14/2022 8:24 am  #2


Re: Extend current in time

WG,
I've wondered the same thing for awhile and you prompted me to look it up.
From the help file:Use tidal streamsWith this feature selected, tidal streams from the tidal databases (see [url=SettingsTides.htm]tide settings[/url]) will be used in the route optimisation. This will override any current GRIB files so be very careful when selecting this feature.The use of tidal streams slows route optimisation, so if you are using a custom grib file for currents, routing away from any tidal stream data or across ocean an ocean, it may pay to turn this off.Tidal stream data is used in preference to grib current data where both are present. So for example in a Newport to Bermuda race, Expedition will use tidal stream predictions to start with then start using your grib data containing Gulf Stream information when you get away from land.

Ironic it even mentions NBR this week!
And good luck with 'tests' tomorrow for all the NBR racers!
Cheers,
Ernie
 
 

 

6/14/2022 3:36 pm  #3


Re: Extend current in time

Thanks Ernie.  Couple points ...

What I've been calling a 24 hr GRIB is actually just a single point in time.  I confirmed this with Predict Wind Offshore App.

I went into Exp Tide Settings and disabled everything.   Still no joy.  Substantially different optimize results from the single point GRIB (looks to be incorrect) versus the 7 day GRIB (correct). 

Cheers

Last edited by WoobaGooba (6/14/2022 6:55 pm)

     Thread Starter
 

6/14/2022 11:14 pm  #4


Re: Extend current in time

You might get an idea by looking at the set & drift values in the routing output.

Maybe send me the two grib files and a route.

Last edited by Nick (6/14/2022 11:15 pm)

 

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