Re: grib2 decoder

• To: Jim Cowie <cowie@xxxxxxxx>
• Subject: Re: grib2 decoder
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Mon, 3 Jan 2005 16:05:54 -0700 (MST)

On Mon, 3 Jan 2005, Jim Cowie wrote:

Hi Robb,

I saw in one of your emails last month a mention that the new
gribtonc decoder (for grib2) was going to be released pretty soon.
Can you tell me when? We are antsy to try it. Thanks,

jim,

good news and bad news. the good news is the decoder has been developed
and tested, the bad news is the resulting netCDF files are huge. the large
file size is the main reason for the delay. the expansion for the files have
a range from 1:20 to 1:50  on average. for example:

NDFD  12.4 megs -> 626.9 megs
eta2  16.3 megs -> 668.5 megs

a couple reasons, the netcdf file is not optimized and the more missing
values in the data the larger the expansion. also the complex packing
scheme permits more variables and levels. john and i have been working
together to leave the files in the grib2 format and to extract the data in
an on demand process.  to implement this, the grib files are scanned to
create an index of products and grid informations. his programs reads
the index and presents the information to the user.  it works well. here's
an url to down load ToolUI program.

http://my.unidata.ucar.edu/content/software/netcdf-java/v2.2/webstart/index.html

in a nutshell,

click viewer  then open a grib2 file
click geogrid  then open the same grid file  geogrid boxes should be
  checked
click view  to access a sanity type view of the variables.

ToolUI currently  doesn't do grids with multiple GDS or thin grids, we are
working on those features now.


i'll probably be only available by email tomorrow if you have
questions then i'll be on PTO for a week.

robb...

-jim

--
Jim Cowie
NCAR/RAL
cowie@xxxxxxxx
303-497-2831

==============================================================================
Robb Kambic                                Unidata Program Center
Software Engineer III                      Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx                   WWW: http://www.unidata.ucar.edu/
==============================================================================