Quasi/thin grib 1 grids

• To: Simon.Elliott@xxxxxxxxxxxx
• Subject: Quasi/thin grib 1 grids
• From: Robb Kambic <rkambic@xxxxxxxxxxxxxxxx>
• Date: Wed, 21 Feb 2007 15:40:29 -0700 (MST)

Hi Simon,

Can you point me to the GRIB1 documentation for eumetsat.  It seems to be
a little different then the NCEP documentation for the GDS, especially for
the Quasi/Thin grid processing.

The problem details for a Quasi Grib1 grid from center 98

In the GDS:
i know octet 5 != 255 means that this is a quasi grid. The information for
the number of points is at the end of the GDS section. For NCEP grids, i
get the number of parallels from the nx or ny depending on the scan mode.
Then i read in the points using readUnsignedShort() for the values. This
works for NCEP thin gribs, but ECMWF thin gribs give numbers in the
1000's. i know that is not correct. if i would use 3 octets to read in the
values, the read would go past the length of the section. This doesn't
seem correct either.  i must be missing something here

GDS NV = 122  octet 4
GDS PL = 33  octet 5
GDS length =520
GDS  numPts = 181
GDS  numPV[ 0 ] = 0
GDS  numPV[ 1 ] = 0
GDS  numPV[ 2 ] = 16916
GDS  numPV[ 3 ] = 0
GDS  numPV[ 4 ] = 16934
GDS  numPV[ 5 ] = 27875
GDS  numPV[ 6 ] = 16959
GDS  numPV[ 7 ] = 42454
GDS  numPV[ 8 ] = 16991
GDS  numPV[ 9 ] = 41744
GDS  numPV[ 10 ] = 17030
GDS  numPV[ 11 ] = 31674
GDS  numPV[ 12 ] = 17076
GDS  numPV[ 13 ] = 38296



Thanks,
Robb...

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