Wind on VR
Post by iconPost by Tigrou26 | 2018-11-02 | 13:38:04

Do you know hox the VR winds are obtained from GFS (NOAA files)?
Does VR use 12h file, 6h file, 3h file ? How do they make the different computation ? Time interpolation and space interpolation between le full degree points ?

commenticon 3 Comments
Post by iconPost by zezo | 2018-11-02 | 15:13:34
3 hour GFS, 1 degree resolution, temporal and spatial interpolation.

Data comes in the original U/V form, temporal interpolation is linear in that space.
Post by iconPost by Tigrou26 | 2018-12-27 | 16:25:26
hello Cvetan

I need some more information on how VR uses the GFS wind

1. the GFS time for GFS is UTC time : does VR use exactly these wind values u,v dated UTC 0,6,12,18 but with the time of the game 1,7,13,19

2. if we admit the item 1 above, I would to know how they go from Oh UTC prediction to 6h UTC prediction when this last one begin to be known at 3h30 UTC
Do they wait till 5h UTC when all the value will be known and transfered by NOAA to commute from the last prediction to the new prediction ?
When they decide to make this commutation do they make a step or linear application of the differencies , at which time and durind what duration ?

Thank you for your answer


Post by iconPost by zezo | 2018-12-27 | 17:03:15
0) The data sent to the client is not exact UV values. It's subjected to a formula involving square root and constant factor. Not sure if the server uses the same data or the original numbers.

1) Game interface runs in user local time now, so it's 01 for you, 02 for me and 00 for someone in UK, so let's stick with UTC.

2) When applying the new GFS there is interpolation between the old one and the new one for the same moment in time.

Like, the weather for 00 UTC is interpolation between 12z+12 and 18z+6. Not just average, but weighted according the exact moment in time. The resulting number is then interpolated again with the 12z+9 data to get the exact conditions.

The above statement is not 100% verified because I never bothered to reimplement it with 100% accuracy.

It won't be very hard to pinpoint the exact implementation details, but you have to do it for the client and server separately.

One possible approach to check the server calculations is to get a test boat parked with TWA 0 at exact integer degree position, preferably somewhere with unstable weather and log the server-side wind data with the extension.
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