space products

[Robb Kambic]

On Fri, 17 Nov 2006, Simon Elliott wrote:

> Hi all,
>
> 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.

Hi Simon,

First, let me thank you for your time. There's no problem decoding the
(HP GRIB.001) file with my decoder that is  803521 bytes long. The file
that was originally sent was not 803521 bytes, but  804420 bytes long.
When the file was edited, the editor inserted extra bytes into the
file. This caused the decoder to get confused and it could not extract the
data. As you know the GRIB format is very rigid, so one extra byte can
change the course of action of the decoder. There was some confusion about
the acquistion of the file and I was unawared that the file was edited, so
I assumed that there was some EUMETSAT changes in the file. Since the
EUMETSAT datasets are very important to our community, I made an
effort to decode the file with the extra bytes. When debugging, I added
some code to accomodate the extra bytes but the decoder still got confused
about the data extraction process. When I got an uncorrupted file, my
decoder work without a problem.


There is one question, the level information is using level 0, is that
correct?

           First Surface Type : 0 Reserved
           First Surface value : 0.0
           Second Surface Type : 0 Reserved
          Second Surface value : 0.0

I have never run across a model using these values before, can you give
some insight?

Thanks,
Robb...

Here's a dump of the Header information of the file, is there an problem
here?

--------------------------------------------------------------------
                        Header : GRIB2
                    Discipline : 3 Space products
                  GRIB Edition : 2
                   GRIB length : 803521
            Originating Center : 254 EUMETSAT Operation Centre
        Originating Sub-Center : 0
Significance of Reference Time : 3 Observation time
                Reference Time : 2006-01-02T11:45:00Z
                Product Status : 1 Operational test products
                  Product Type : 6 Processed satellite observations
         Number of data points : 1530169
                     Grid Name : 90 Space View Perspective or Orthographic
                     Grid Shape: 3 Earth oblate spheroid with axes
specified by
producer
        Oblate earth major axis: 6378.14
        Oblate earth minor axis: 6356.7554
Number of points along parallel: 1237
Number of points along meridian: 1237
Latitude of sub-satellite point: 0.0
  Longitude of sub-satellite pt: 0.0
  Resolution & Component flags : 0
         i direction increment : 1188.0
         j direction increment : 1187.0
 X-coordinate of sub-satellite : 619.0
 Y-coordinate of sub-satellite : 619.0
                 Scanning mode : 192
                   Basic angle : 0
        Altitude of the camera : 7.4533146E8
        X-coordinate of origin : 0.0
        Y-coordinate of origin : 0.0
            Product Definition : 30 Satellite product
            Parameter Category : 1 Quantitative_products
                Parameter Name : 2 Cloud_Top_Height
               Parameter Units : m
       Generating Process Type : 8 Observation
                  ForecastTime : 0
            First Surface Type : 0 Reserved
           First Surface value : 0.0
           Second Surface Type : 0 Reserved
          Second Surface value : 0.0
--------------------------------------------------------------------
                        Header : GRIB2
                    Discipline : 3 Space products
                  GRIB Edition : 2
                   GRIB length : 803521
            Originating Center : 254 EUMETSAT Operation Centre
        Originating Sub-Center : 0
Significance of Reference Time : 3 Observation time
                Reference Time : 2006-01-02T11:45:00Z
                Product Status : 1 Operational test products
                  Product Type : 6 Processed satellite observations
         Number of data points : 1530169
                     Grid Name : 90 Space View Perspective or Orthographic
                     Grid Shape: 3 Earth oblate spheroid with axes
specified by
producer
        Oblate earth major axis: 6378.14
        Oblate earth minor axis: 6356.7554
Number of points along parallel: 1237
Number of points along meridian: 1237
Latitude of sub-satellite point: 0.0
  Longitude of sub-satellite pt: 0.0
  Resolution & Component flags : 0
         i direction increment : 1188.0
         j direction increment : 1187.0
 X-coordinate of sub-satellite : 619.0
 Y-coordinate of sub-satellite : 619.0
                 Scanning mode : 192
                   Basic angle : 0
        Altitude of the camera : 7.4533146E8
        X-coordinate of origin : 0.0
        Y-coordinate of origin : 0.0
            Product Definition : 30 Satellite product
            Parameter Category : 1 Quantitative_products
                Parameter Name : 3 Cloud_Top_Height_Quality_Indicator
               Parameter Units :
       Generating Process Type : 8 Observation
                  ForecastTime : 0
            First Surface Type : 0 Reserved
           First Surface value : 0.0
           Second Surface Type : 0 Reserved
          Second Surface value : 0.0


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