all.grb question
Post by iconPost by fab | 2020-12-22 | 08:44:48

Hi Cvetan,

I noted a difference between all.grib ( GFS 1° ) and the game interface.
I checked the values at integer points. ie with no interpolation.

I suppose a rounding process made by VR.

Have you informations about this process.

IMO : speeds are converted to km/h ( 1 decimal ) and angles are integer. Low speeds are 2 Kn min.

Am I right ?

thx for your help.

commenticon 2 Comments
Post by iconPost by zezo | 2020-12-23 | 17:56:41
Speeds are in m/s, GRIB U/V.

But VR uses an encoding to 1-byte signed integer (+/-128). The value is square root of the actual speed, multiplied by a coefficient.

sub vr($) {
my $d = shift;
my $sign = ($d < 0)?-1:1;
return $sign * round(sqrt(abs($d*230.4)));
}

Post by iconPost by fab | 2020-12-23 | 23:19:19
Thanks Cvetan.

I'll try to post process NOAA GRIB in order to integrate this "rounding" procedure,
and maybe increase the resolution 1°->0.5° by applying the interpolation algorithm found in your js.

fair winds.



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