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Old 15-01-2015, 08:16   #1
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Talking New "super gribs" (0.25 spacing) in OpenCpn

Yesterday (Jan 14th), after several months of beta testing, NCEP officialy released its first batch of fine-grained gribs on a 0.25 latitude/longitude grid (instead of 0.5 previously). Also, major improvements in the GFS model have been announced. These gribs are available in the usual grib1 format, but will eventually be available only in the new grib2 format, entailing a major upgrade in the grib plugin.
These 'super gribs' are available in Opencpn with a tiny human involvement:
Using the grib plugin to request a grib from Saildocs, just change both 0.5 spacing parameters to 0.25 in the mail which is ready to be sent...
Here are exemples of the old (0.5) and new (0.25) spacings requested at the same time.
Modifying the grib plugin to allow forwarding a request for the new 0.25 spacing should be a simple upgrade...
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Old 15-01-2015, 08:30   #2
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Cool. Good to know.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
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Old 15-01-2015, 09:41   #3
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Very good.
An upgrade to O needs to a adjust the particle map "particle spacing", for future 0.25 option.

Thomas
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Old 15-01-2015, 20:02   #4
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Thomas...
What do you mean exactly? Particles seem OK to me with a 1/4 degree grib I just got...
The selection of the 0.25 degree GFS gribs is now implemented in https://github.com/nohal/OpenCPN/tree/grib025

Pavel
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Old 16-01-2015, 11:57   #5
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Quote:
Originally Posted by nohal View Post
Thomas...
What do you mean exactly? Particles seem OK to me with a 1/4 degree grib I just got...
The selection of the 0.25 degree GFS gribs is now implemented in https://github.com/nohal/OpenCPN/tree/grib025

Pavel
Pavel

Good question. Let me rephrase that. Users may want to adjust the particle maps density setting when using 0.25 degrees resolution. I found that with .5 degrees resolution, the default setting, midway is OK. With .25 degrees, lowest possible setting suited me better.
Also, the higher resolution requires more from the processor, runs slower on my semi-old box. The download is also bigger.

Thomas
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Old 16-01-2015, 12:17   #6
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Thomas...
Ah, OK. So no code needed, good
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Old 16-01-2015, 12:32   #7
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Re: New "super gribs" (0.25 spacing) in OpenCpn

BTW for the mediterranean you get 0.1 gribs from OpenSkiron OpenSkiron - Home
Works in OpenCPN as well.
Gerhard
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Old 17-01-2015, 07:47   #8
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Re: New "super gribs" (0.25 spacing) in OpenCpn

Quote:
Originally Posted by nohal View Post
The selection of the 0.25 degree GFS gribs is now implemented in https://github.com/nohal/OpenCPN/tree/grib025

Pavel
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Old 22-01-2015, 01:24   #9
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Re: New "super gribs" (0.25 spacing) in OpenCpn

I would like to test it, if we get it compiled for windows.

Regards, Lars
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Old 22-01-2015, 04:17   #10
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Re: New "super gribs" (0.25 spacing) in OpenCpn

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Originally Posted by cagney View Post
The download is also bigger.

Thomas
4 times, which is not irrelevant. I wander if the free providers will be happy.
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Old 28-01-2015, 14:09   #11
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Re: New "super gribs" (0.25 spacing) in OpenCpn

One more thing needs to be looked at in the grib plugin.
With the new gribs the forecast horizon is extended from 8 to 10 days ahead.

For example this, manually adjusted, request:
Quote:
send GFS:60N,55N,7E,17E|0.25,0.25|0,3,6..240|=
WIND,PRESS,APCP,TCDC,AIRTMP,HTSGW,WVPER,=
WVDIR,SEATMP,CAPE
Resulted in a grib for 10 days, including wave data and weather table.
The choices and the warning dialog needs adjusting accordingly.

Here is the official release message for the updated GFS grib format.
http://www.nws.noaa.gov/om/notificat...-46gfs_cca.htm

Thomas
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Old 29-01-2015, 13:51   #12
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Re: New "super gribs" (0.25 spacing) in OpenCpn

OK Thomas
I read the release, and I do not understood all, but the necessary change will be done as soon as the development activity will re-start.
Jean Pierre
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Old 02-02-2015, 11:35   #13
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Re: New "super gribs" (0.25 spacing) in OpenCpn

That sounds good.
In the current version the grib download request window doesn't allow straddling the 180 degree meridian, which unfortunately is where I sail !
If I try to request a Grib that goes from say 150W to 165E, it tells me that max lon. is less than min lon.
It seems that the lon. has ti be the same "sign" either E or W but not both.
Is there a "fix" for that, or some way to get around it ?
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