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Old 04-09-2013, 06:32   #1
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grb2 files for tidal info

Hi,

In another post it is mentioned to use grb2 files, downloaded from a German site, for tidal information. Having Opencpn running on Windows 7, how can I open these files?

Thanks in advance!
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Old 04-09-2013, 07:11   #2
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Re: grb2 files for tidal info

George...
You can't, BRIB2 format is not supported in OpenCPN yet. You would have to convert them to GRIB1 format or download them in this format directly, if it's still available from BSH.

Pavel
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Old 04-09-2013, 07:24   #3
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Re: grb2 files for tidal info

Pavel…
Thanks for your quick respond. I'll google on how to convert GRIB2 into GRIB1.

I'm still looking for a nice solution to show tidal stream (direction) information in Opencpn.
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Old 04-09-2013, 10:31   #4
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Re: grb2 files for tidal info

Unless going into perl or fortran script, I can't find a Windows program to run to convert GRIB2 into GRIB1 Anyone?
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Old 04-09-2013, 11:09   #5
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Re: grb2 files for tidal info

George64..

qtVlm Route Optimizer promised grib2 compatibility in their next version where you can copy/paste the resulting optimized route in .kml and .gpx format.

Strömungen promised in the meantime to also provide temporary support for the old .grb format,but it has not happened as yet.

Tore
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Old 04-09-2013, 11:18   #6
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Re: grb2 files for tidal info

Thanks Tore.

The don't side is, imho, one always needs an internet connection. Something that can be quite challenging, I know from own experience. That why I was trying to find a way the current direction and strength can be shown in Opencpn easily. So far it seems "VisitMyHarbour" does give a solution by buying their usb dongle with charts as well as it comes with tidal data.

In an other post I read a member managed to use the weatherfax plugin to fetch and show the tidal from Strömungen, however that was on Linux. I assume he also had a script running to convert the fetched GRIB2-file although I'm not sure.
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Old 23-09-2013, 08:29   #7
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Re: grb2 files for tidal info

From Tore:

I am pleased to advice that European Stream data is now also available in the old .grib format (.grib1) parallel with .grib2 until the major navigation programs have time to upgrade to the new format. Thanks to Kai at Operational Model System of the BSH in Hamburg:
ftp://ftp.bsh.de/Stroemungsvorhersagen/grib1/
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Old 23-09-2013, 12:08   #8
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Re: grb2 files for tidal info

gleason..

Using the latest v. 3.3.814 of OCPN has anyone tried the newly available stream grib1 files? After re-naming the file to .grib I can only get to display the stream direction arrows but not the compass direction and speed in knots of the stream. Nor are any temperature colors displayed. See attached.
Do you get the same?

Tore
Attached Thumbnails
Click image for larger version

Name:	stream grib no.png
Views:	115
Size:	130.6 KB
ID:	67767  
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Old 23-09-2013, 14:22   #9
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Re: grb2 files for tidal info

Tore,
did you ever read the hint at the left bottom of your screenshot?

Gerhard
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Old 23-09-2013, 14:26   #10
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Re: grb2 files for tidal info

Gerhard..

Makes no difference in this case I am afraid...

Tore
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Old 24-09-2013, 07:31   #11
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Re: grb2 files for tidal info

FYI ...

Quote:
Kai..

OK,I understand it is a complex system which can not be converted EXACTLY to the old .grb format,making it incompatible to both Fugawi ENC 4.5 as well as the qtVlm Route Optimizing program,AND as far as I can make it,partially incompatible also with OCPN. The popular,Android based OruxMaps is also not able to read the converted .grb format. BUT,if that´s a good as it can get,in the meantime,until the various nav. progs catch up with the new version .grb2, at least we have some streaming facility in OCPN,and thank you for making that available.

I will pass on your U and V format description to the creators of qtVlm but I doubt if they will make any complicated changes only as a temporary stop gap.

Thanks for taking the time to explain.

Regds
Tore
----------------------------------------------
Tore,

As I mentioned in an earlier post, the two files are different in terms of time of forecast:Grib format has a dedicated time field called reference time in the Product Definition Section octets 13-17.

Further there is in octet 18 a forecast time unit defined (ie. Year or month… or minute) in octets 19 and 20 there is a timeinterval defined in units of octet 18 .

The old format has octets 13-17 step up by 30 minutes for each forecast timestep, i.e first U and V records have date00:30, Second have date01:00 …
The new format has for the whole file octets 13-17 be constant date00:00 and increment octets 19 and 20 such that each pair (U,V) has an additional 30 minutes timestamp.

This can explain the fact that the routing program does not accept the new format ( I found a Grib Package from a Science Institution which can not handle the minutes time intevall either).

Regards
Mit freundlichen Grüßen
Kai Jancke
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