Re: decoders] Grib File Data Extraction

On Mon, 4 Aug 2008, Don McGregor wrote:

> I'm having problems spotting the necessary information in the indexer output.
>
> I ran the indexer and got the output attached at the end.
>
> Presumably this contains the necessary data for input to Grib1GetData,
> namely the byte offset,
>
> Grib1GetData [gribFile] [byte offset] [scale] [BMSExists]

Don

on the decoders page

http://www.unidata.ucar.edu/software/decoders/grib/javadoc/IndexFormat.txt

section 3  gives the definition of all the fields.


for your data example with your index

java -Xmx256m ucar/grib/grib1/Grib1GetData <datafile> 54 2 false


there is also a toolsUI program at:

http://www.unidata.ucar.edu/software/netcdf-java/

that will let display or look at the data values, it's a in-house tool so 
the documentation is sparce.

Robb...




> But I can't spot the offset for the data section in the output of the 
> indexer.
> Where is it?
>
>
> Indexer output:
>
> index_version = 6.0
> grid_edition = 1
> location = data/seaTemp1
> length = 390002
> created = 2008-08-04T17:16:15Z
> center = 58
> sub_center = 0
> table_version = 3
> tiles = 1
> thin = false
> ensemble = false
> --------------------------------------------------------------------
> 0 0 -1 80 78 1 0.0 255 0.0 2008-07-30T12:00:00Z 0 24011925 54 390002 2 false 
> 58 0 3
> --------------------------------------------------------------------
> GDSkey = 24011925
> grid_type = 0
> grid_name = Latitude/Longitude Grid
> grid_shape_code = 0
> grid_shape = spherical
> grid_radius_spherical_earth = 6367.47
> Nx = 720
> Ny = 361
> La1 = -90.0
> Lo1 = 0.0
> ResCompFlag = 128
> Winds = Relative
> La2 = 90.0
> Lo2 = -0.5
> Dx = 0.5
> Dy = 0.5
> ScanningMode = 64
>
>
> I want to extract data from the data record. Presmumably the Grib1GetData
> class does this.
>
>
> On Aug 2, 2008, at 8:57 AM, Robb Kambic wrote:
>
> > On Fri, 1 Aug 2008, Don McGregor wrote:
> >
> > > I'm looking for some examples of extracting data from grib files using
> > > the Java decoders.
> > > The Grib1Dump utility shows the output at the bottom of this message.
> > > However, when I
> > > load the file using the code below, I get zero records. I'm new to
> > > grib files, and my understanding
> > > is that there should be a record for each parameter.
> >
> >
> > Hiya,
> >
> > GribDump is just to dump the headers of the Grib files, most Grib data is 
> > large so we use the index approach and a utility GribGetData ie
> >
> > Grib(1|2)Indexer to index the records in the Grib file
> >
> >
> > # Grib(1|2)GetData to extract the data on a parameter basis.
> > # Parameter and level lookup routines. See Parameters
> >
> > on the page:
> >
> > http://www.unidata.ucar.edu/software/decoders/
> >
> > there are Java docs that explain the routines in detail and what parameters 
> > to use.
> >
> > Robb...
> >
> >
> > >             ucar.unidata.io.RandomAccessFile raf = new
> > > ucar.unidata.io.RandomAccessFile("data/seaTemp1","r");
> > >             Grib1Input gribInput = new Grib1Input(raf);
> > >             System.out.println("GRIB version is " +
> > > gribInput.getEdition());
> > >
> > >             List records = gribInput.getRecords();
> > >             System.out.println("Number of records is " +
> > > records.size());
> > >
> > > Dump of the GRIB file:
> > >
> > >                       Header : GRIB1
> > >                   Discipline : 0 Meteorological Products
> > >                 GRIB Edition : 1
> > >                  GRIB length : 390002
> > >           Originating Center : 58 U.S. Navy Fleet Numerical
> > > Meteorology and Oceanography Center
> > >       Originating Sub-Center : 0 WMO Secretariat
> > >           Product Definition : 0 Forecast/Uninitialized Analysis/
> > > Image Product
> > >           Parameter Category : -1 Meteorological Parameters
> > >               Parameter Name : 80 var80 temperature of sea  water
> > >              Parameter Units : deg_K
> > >               Reference Time : 2008-07-30T12:00:00Z
> > >                   Time Units : hour
> > >         Time Range Indicator : product valid at RT + P1
> > >                  Time 1 (P1) : 0
> > >                  Time 2 (P2) : 0
> > >      Generating Process Type : 78 126 wave triangular, 28 layer
> > > Spectral model from Medium Range Forecast run
> > >                   Level Type : 1 surface
> > >                Level Value 1 : 0.0
> > >                Level Value 2 : 0.0
> > >                   GDS Exists : true
> > >                   BMS Exists : false
> > >        Number of data points : 259920
> > >                    Grid Name : Latitude/Longitude Grid
> > >                    Grid Shape: 0 spherical
> > >        Spherical earth radius: 6367.47
> > >                           Nx : 720
> > >                           Ny : 361
> > >                          La1 : -90.0
> > >                          Lo1 : 0.0
> > > Resolution & Component flags : 128
> > >                        Winds : Relative
> > >                          La2 : 90.0
> > >                          Lo2 : -0.5
> > >                           Dx : 0.5
> > >                           Dy : 0.5
> > >                Scanning mode : 64
> > >
> > >
> > > _______________________________________________
> > > decoders mailing list
> > > address@hidden
> > > For list information or to unsubscribe,  visit: 
> > > http://www.unidata.ucar.edu/mailing_lists/
> >
> > ===============================================================================
> > Robb Kambic                                Unidata Program Center
> > Software Engineer III			   Univ. Corp for Atmospheric 
> > Research
> > address@hidden             WWW: http://www.unidata.ucar.edu/
> > ===============================================================================

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