Re: space products

• To: Simon Elliott <Simon.Elliott@xxxxxxxxxxxx>
• Subject: Re: space products
• From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
• Date: Fri, 17 Nov 2006 08:40:53 -0700

Hi Simon-

Simon Elliott wrote:

WHen I look at the file attached by HansPeter (HP GRIB.001) it looks fine to 
me.  The GRIB part can be found after the first 899 bytes.  The remaining part 
(GRIB to 7777, inclusive) is 803521 bytes long, which is as indicated in octets 
9 to 16 of Section 0.

I'll work with Robb on this next week.  I think he made some changes to skip 
the header, but I don't have access to his changes so it still fails in what I 
have.

The users who have been looking at the data have received it via EUMETCast, and 
also via ftp from me.  Maybe some got data from the UMARF, but I don't get to 
hear about them.  I think that as long as a decoder looks through a file and 
pulls out GRIB (or BUFR) messages before decoding, then it doesn't matter how 
they are packed into files.

I agree in principle.  It's fine if you are passing a file to a decoder and are 
assured that the decoder is a GRIB decoder and that the user says that there is 
a GRIB message in the file.  However, in our case, we have a top level data 
handler that has to determine which decoder to pass it to. This top level 
handler can open netCDF files, GRIB1, GRIB2, OPeNDAP remote URLs, etc.  So, it 
has to make some determination at the start about what is in the particular 
file.  Usually, it does this by looking at the first few bytes of a file.  For 
a netCDF file, it looks for the netCDF header, for a GRIB file, it looks for 
GRIB1 or GRIB2. The question is how far into the file do you look before giving 
up?  Also, should a decoder have to handle both GRIB and BUFR in the same file?

Anyway, we'll wait for Robb's return and work on this more at that time.

Thanks for your help and input.

Don
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
*************************************************************

• References:
  • Re: space products
    • From: Simon Elliott