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Rasbats · 27-01-2016, 07:01

First posting to avoid re-inventing the wheel.

If anyone has been working on decoding Grib2 for OpenCPN please can you add a post to this thread.

Initial work for oGrib2 has been aimed at decoding Grib2 files of tidal current data from the German BSH:

StrÃ¶mungen

The Grib2 plugin from Pavel/Konni was used as a template (thanks again Pavel). A different approach was taken for accessing the data.

For reading the messages in the file the grib_api library from the ECMWF has been used:

https://software.ecmwf.int/wiki/display/GRIB/Home

The lib is open-source and very well documented. Tools can be built (grib_ls, grib_dump etc) for an initial look at the contents of the Grib file.

A lot of work will be needed to extend the plugin for met fields but I think using grib_api could have a lot of benefits. GRIB edition 1 and edition 2 are both accessed using the same key names/values approach.

Mike

rgleason · 27-01-2016, 19:16

Cool! How nice.
Can Jean Pierre, Sean and others's work be used with it?
Thank you for moving Pavel's work forward!
Rick

Gilletarom · 02-02-2016, 15:08

Hello rasbats,

Quote:

Originally Posted by Rasbats

First posting to avoid re-inventing the wheel.
If anyone has been working on decoding Grib2 for OpenCPN please can you add a post to this thread.
...
StrÃ¶mungen
..... GRIB edition 1 and edition 2 are both accessed using the same key names/values approach.
Mike

In any case,, I just downloaded one of these files Grib version 1 and the OCPN Grib plugin displays very well the these grib1 files.

Rasbats · 03-02-2016, 04:29

G,

Tidal current GRIBs (version 1) from Index of /MyOcean only display the first entry. I am unable to step through the time series in the GRIB. Only the current for the first time is shown. This is for OpencPN 4.1.1329 on both Linux and Windows 8.1.

I have added a task for this in Flyspray.

For the tidal current GRIBs from bsh: ftp://ftp.bsh.de/Stroemungsvorhersagen/ The bsh GRIB for the North Sea/Channel(to Start Point) is only available in GRIB2 format.

Météo-France GRIB files are now available for free but only in GRIB2 format.

Mike

Gilletarom · 03-02-2016, 06:39

Hello Rasbats,

I do not understand your problem. I feel that the time slots can be displayed.

For cons, I found a strange bug with the file "Global". I've already alerted Jean Pierre about it. But he could not take the test because it is currently a bad internet access.

If you could try it and tell me if you see something strange with a "de-zooming" slipped up making the display from left to right and from right to left, for example by standing at 0 ° longitude or 180 ° longitude with your mouse. See also when your mouse go throught the axe of screen ...

Best regards. Gilletarom.

Rasbats · 03-02-2016, 08:11

Hello Gérard,

By file "Global" do you mean the world chart outline? Nothing strange seen with this. If not, could you explain the file causing the problems. Is it a GRIB?

I will post some screen shots of the problem with the GRIB plugin and GRIB1 tidal currents.

Best regards,
Mike

Gilletarom · 03-02-2016, 09:45

Hello Mike,

Quote:

Originally Posted by Rasbats

Hello Gérard,
By file "Global" do you mean the world chart outline? Nothing strange seen with this. If not, could you explain the file causing the problems. Is it a GRIB?
I will post some screen shots of the problem with the GRIB plugin and GRIB1 tidal currents.Mike

Sorry, I thought you saw that there was a "global" grib file in index / MyOcean. Try it please.

Rasbats · 03-02-2016, 10:02

Found "Global"!!! You are correct. Panning across the 0 and 180 axes results in the arrows changing direction.

The drop-down for times is working for Global.

I was testing with Bretagne. Could you have a look at the drop-down for that file?

Mike

Gilletarom · 03-02-2016, 10:18

Mike,

Quote:

Originally Posted by Rasbats

I was testing with Bretagne. Could you have a look at the drop-down for that file?
Mike

You are right. With Bretagne, only one time slot. But, perhaps, this is normal ? Perhaps the file is corrupted ? Wait and see.

Rasbats · 03-02-2016, 12:56

Maybe, but when I open the file with my prototype oGrib2 I see several messages. And I can step through those messages, i.e. showing different times.

(With the grib_api from ECMWF both GRIB1 and GRIB2 can be accessed)

Mike

Gilletarom · 03-02-2016, 14:12

Hello Mike,

Quote:

Originally Posted by Rasbats

Maybe, but when I open the file with my prototype oGrib2 I see several messages. And I can step through those messages, i.e. showing different times.
(With the grib_api from ECMWF both GRIB1 and GRIB2 can be accessed)
Mike

Can you explain how to use the software that opens the grib grib 1 and 2?

Thank you beforehand. Gilletarom.

rgleason · 04-02-2016, 04:46

I tried to compile github.com/rasbats/grib2_pi but I think I need the JasPer library or part of it.
Also is this standalone or with O?

Now I see it. It is with O
go to the plugin subdirectory in your tree
clone the plugin repository from githu

Rasbats · 04-02-2016, 05:02

Rick,

You are way ahead of me.

That git is the fork from Nohal. I have not added anything to it!

I had to compile my own Jasper and remove the one from git. Then link in the new Jasper project etc, etc.

Best wait a while.

Mike