Technical help with GRIB format? (yzGrib)

[Eric.]

Hi,

I'm working on project to convert world current data into a grib files.

I've gotten to the point where I want to test the files, but yzGrib won't recognize any of my attempts or the saildocs version as a valid GRIB.

Here's links to the sample files I'm trying to test:

Baseline example file from saildocs.com
http://www.svsarana.com/temp/sample_current.grb

GRIB1 version
http://www.svsarana.com/temp/oscar.grb

GRIB2 Version:
http://www.svsarana.com/temp/oscar.grb2

None of these seem to work on yzGrib. Can someone else test them and see if you can find a problem or if any of them work? The oscar files should be a world simulation result showing direction and speed of current. They are big 3M and 6M.

Any advice on what might be wrong with the GRIB file parameters would be appreciated greatly.

Thanks,
Eric

[Eric.]

I should mention that the sample_current.grb works on OpenCPN but not zyGrib.

Here's a snapshot of the differences between my new grb and the sample. (The sample file also has sea temperature data in addition to current data). Scroll the text to see all the data. The Level and the parameter names are different for starters....

sample_current.grb 
    -1 :       Date     Time   Level Gridsize    Miss :     Minimum        Mean     Maximum : Parameter name
     1 : 2013-01-16 12:00:00       0       66      15 :    -0.26000    0.072745     0.46000 : var49      
     2 : 2013-01-16 12:00:00       0       66      14 :    -0.38000    0.040000     0.58000 : var50      
     3 : 2013-01-16 12:00:00       0       66      14 :      296.07      299.27      300.83 : var80      
cdo infon: Processed 198 values from 3 variables over 1 timestep ( 0.01s )

oscar.grb
    -1 :       Date     Time   Level Gridsize    Miss :     Minimum        Mean     Maximum : Parameter name
     1 : 2013-01-11 00:00:00      15   577681  251085 :  0.00066114      182.13      360.00 : var1       
     2 : 2013-01-11 00:00:00      15   577681  251085 :  0.00018081     0.16572      3.0767 : var2       
cdo infon: Processed 1155362 values from 2 variables over 1 timestep ( 0.16s )

[Albro359]

Eric, I can open your oscar.grib in Maxsea, but all it gives is pressure in colour and very crudely..ie no isobars
Sorry I can't help any further
Cheers
Alan

[hwecken]

To open the current gribs in qtvlm was not possible

[Eric.]

Thanks for the help. I think there must be a problem with yzGrib and current values.

However my files did have some formatting problems putting the current layers on the pressure grid and a few other issues that I think I fixed in this version. In fact I can get this file to open without errors in openCPN however no data is visible.

Can anyone view the current data on this grib?
http://www.svsarana.com/temp/grib3.grb

[sailorF54]

Zygrib: failure (Ugrib too, but that's different)
OpenCpn: very partial view with old plugin, nothing with current plugin.
Airmail-Viewfax: the best of the lot (partial world-wide view, very slow zoom to Bay of Biscay (Atlantic France and Spain). Hangs at further zoom level.

[Eric.]

Thanks and bonus points for the screen shots! At least I'm making some progress. The files are pretty memory intensive so they will run slow since it's the whole globe.

Perhaps if I put the current data in as a wind layer it would be more universally accepted, even if incorrect.

I'll have to work on this some more. Hopefully when I'm finished I can get saildocs to add this service to their catalog. Thanks again. I'll probably be back again soon for some more tests.

Eric

[sailorF54]

You could have a look at the Grib2 format of the North Sea currents
Strömungen
linking to
ftp://ftp.bsh.de/Stroemungsvorhersagen/

[Eric.]

Originally Posted by sailorF54

You could have a look at the Grib2 format of the North Sea currents

Have you found these files to work in most viewers?

I'm only using grib1 because I thought it would be more compatible. Perhaps for current overlays that is a bad assumption.

EDIT: By the way, I've put a smaller data sub-set for testing which is just an area in the Caribbean. This smaller data file should be more representative of how people would use it instead of the full planet:
http://www.svsarana.com/temp/grib5.grb

FYI -- My version (5.0.56) of airmail's viewfax won't read GRIB2

[sailorF54]

There are classical gribs in the 'archiv section' that could give you a clue. These can be opened with Opencpn and airmail-viexfax (but not with zygrib: you could ask the author. He's known to be reactive)
Grib5 (Carib zone) opens fine with airmail-viewfax only
Zooming in and out is fast...