[gdal-dev] grib driver

[winkey]

After trying a second time I finally got the grib driver to work for me.

the grib file i am testing with is the gfs forecast model .5 degree
global grid available from
http://www.ftp.ncep.noaa.gov/data/nccf/com/gfs/prod/gfs.2008011412/gfs.t12z.pgrb2f00

replace 2008011412 with current date, last 2 digits are hour 00, 06, 12,
18

this is a list of my experiences.

first with gdalinfo I noticed that not enough info was reported to
choose the band(s) you want

degrib reports:
 2.0, 158408, 2, TMP="Temperature [K]", 1000-ISBL, 11/05/2007 00:00,
11/05/2007 00:00, 0.00

gdalinfo reports:
Band 2 Block=720x1 Type=Float64, ColorInterp=Undefined
  Description = 1000[Pa] ISBL="Isobaric surface"


There seems to be no way to specify the units. degrib has a feature to
convert the values in the grid to english or metric units. For instance
in the band above default would have the values in kelvin, specifying
english would convert those values to Fahrenheit, and metric would
convert to celsius.


Two part messages seem to be represented by two different bands. This is
not necessarily a problem but without the variable name being reported
by gdalinfo it is hard to find what your looking for.

degrib reports:
8.0, 901490, 2, UGRD="u-component of wind [m/s]", 2000-ISBL, 11/05/2007
00:00, 11/05/2007 00:00, 0.00
8.1, 901490, 2, VGRD="v-component of wind [m/s]", 2000-ISBL, 11/05/2007
00:00, 11/05/2007 00:00, 0.00

gdalinfo reports:
Band 8 Block=720x1 Type=Float64, ColorInterp=Undefined
  Description = 2000[Pa] ISBL="Isobaric surface"
Band 9 Block=720x1 Type=Float64, ColorInterp=Undefined
  Description = 2000[Pa] ISBL="Isobaric surface"


I tried contouring band 169 (aka grib msg 147) 925 mb temps it seemed to
contour only the northern hemisphere and nothing seemed in the right
place. once again I may have the wrong band, but that would not effect
hemisphere only the contours


thanks

brian