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My goal is to extract wind information from data provided to me in the GRIB2 format as it has been done in the attached image.

I was curious if anybody had any experience with this format. I'm not sure if I am going in the right direction or what format I should be exporting it to. My end goal is to display this information through openlayers. So far, I have used gdal_translate to extract specific information ex. Temperature from band 25 (see command below).

gdal_translate -of Gtiff -b 25 weather.grib2 band25.tiff

I also have access to FME Desktop professional edition.

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So does your gdal_translate command work? What does the output data look like in a GIS such as Quantum? –  MerseyViking Jan 31 '12 at 17:01
    
MerseyViking, it does work and exports my file as a Geotiff. My problem is understanding the values. According to ogrinfo, band 25 should be temperature in Kelvin. However, when I look at the exported GeoTiff, I see negative values, which should be impossible. Here is my gdalinfo stats result and corresponding Geotiff dl.dropbox.com/u/2375551/20120130_0600f30.grib2.aux.xml dl.dropbox.com/u/2375551/band25.tiff –  user5584 Jan 31 '12 at 18:20
    
Negative Kelvin is very odd. There is either an error with the data, or a bug in GDAL. Is the GRIB file online? Is is possible to recompute the statistics with, e.g., code.google.com/p/pygrib? –  Mike T Jan 31 '12 at 19:35
    
Thanks for the help Mike. If you want to see the grib2 file, I have uploaded it here: dl.dropbox.com/u/2375551/20120130_0600f30.grib2 –  user5584 Jan 31 '12 at 20:03
    
This is an old post, but I wanted to address the temperature issue noted by the original poster. Since GDAL 1.9.0 the grib support has automatically done unit conversions by default. See this link for more information, including how to override this default: gdal.org/frmt_grib.html –  hcarty Jun 12 at 1:32

1 Answer 1

up vote 2 down vote accepted

I was able to figure out my issue

I used the WGRIB2 utility in order to convert my GRIB2 data to a CSV and subsequently into my POSTGIS database. I used the following command to take the VGRD, UGRD, and TMP at 100mb:

wgrib2 -match ":(VGRD|UGRD|TMP): 100mb" weather.grib2 -lon lon1 lat1 -csv csvfile

I then loaded my CSV to my POSTGIS database and overlayed it on top of my baselayer.

Here is my final result for my temperature layer at 100mb http://i.imgur.com/KEnz0.jpg

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Diego! Can you give some more details on this issue? How do you load your csv to postgis and generate point geometry? I'm doing this: wgrib2 -match "(:TMP:surface:anl:|:TMP:2 m above ground:anl:)" gfs.t00z.sfluxgrbf00.grib2 -csv fcast.csv COPY tmp (begindate, enddate, name, name2, value, lat, lon) FROM '/Users/nl/Work/ncep/fcast.csv' WITH DELIMITER ',' CSV; SELECT addGeometryColumn ('public', 'tmp', 'the_geom', 4326, 'POINT', 2); UPDATE tmp SET lon = lon-360 WHERE lon > 180; UPDATE tmp SET the_geom=ST_SetSRID(ST_MakePoint(lat,lon), 4326); And I get a strange result: dl.dropbox.com/u... –  Nick Apr 9 '12 at 9:27
    
Hi Nick, I used ogr2ogr -f "PostgreSQL" PG:"host=127.0.0.1 user=postgres dbname=databasename" yourcsv.csv –  user5584 Apr 10 '12 at 18:29

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