Chad,
Thanks for pointing out that the Java Docs need to be updated on the
Decoders page, I'll do it sometime this afternoon.
Robb...
On Mon, 14 Sep 2009, Chad Saxon wrote:
Robb,
thanks for the input and feedback. i went ahead and got the grib-8.0 library
and have to work through some of the depreciated stuff in my code now but i
was wondering the the javadoc reflects the grib 8.0 changes? Some of the
functionality like, for example, Grib1GridDefinitionSection.getGdsVars();
doesnt appear in the API javadoc that i am looking at.
thanks...
Chad
On Sep 8, 2009, at 2:03 PM, Robb Kambic wrote:
On Mon, 7 Sep 2009, Chad Saxon wrote:
I am writing some low level code(because i need to),
to read grib files and all the values that i print out
on the console do not match the values when i dump
them out to a file. The grib file that i am testing
against is including in this e-mail for those that
want to take a look.
Also i seem to be having problems getting actual
String literals for certain codes.. like the parameter
name for code 11 is Temperature and the Unit type is K
in this case but it seems that the way to get these
are not very intuitive to get using Index and my
GribRecords variable in the code below. Maybe someone
could shed some light on this??
In advance, i want to thank all those that can take
the time to look through this.
--Chad
Chad,
The Grib library usually reads the records of the grib file in
sequence of the sections, there are 5 sections to Grib1. See:
http://www.nco.ncep.noaa.gov/pmb/docs/on388/
To read a particular section, the filePointer must be moved to the
start of the section to have a proper read. There is an index file
that has some of the offsets to the sections, such as the GDS
section. Here's the index of your sample file:
------------------------------------------------------------------
10 0 -1 11 96 1 0.0 255 0.0 2009-09-07T06:00:00Z 24 284494432 36
68 1 false 7 0 2
10 0 -1 11 96 1 0.0 255 0.0 2009-09-07T06:00:00Z 48 284494432 390
422 1 false 7 0 2
10 0 -1 11 96 1 0.0 255 0.0 2009-09-07T06:00:00Z 72 284494432 744
776 1 false 7 0 2
------------------------------------------------------------------
The offsets 36, 390, and 744 are the GDS offsets for the 3 records
in the file. If you would modify you code to do the seeks and then
read the GDS, then the values will be correct.
gribfile.seek( 36 );
Grib1GridDefinitionSection gds =
Grib1GridDefinitionSection(gribfile);
Here are some files that will help you understand the how the
index works.
IndexFormat.txt locate in the root directory of the package.
ucar/grib/grib1 directory:
Grib1WriteIndex.java
Grib1Dump.java
Grib1GetData.java
Grib1Data.java
Grib1Input.java
also look at the following files on how to extract particular PDS
and GDS values;
GribReadIndex.java
ShowGribIndex.java
I must warn you that the Grib library has been refactored, so the
Index api will be slightly different then the 6.0 release. I would
suggest that you get the latest 8.0 release on the decoders page
located at:
http://www.unidata.ucar.edu/software/decoders/
Robb...
here is my code below with output:
public class GribPlugin {
java.io.PrintStream ps;
String[] fileDump;
Grib1GridDefinitionSection gridSection;
String testfile = "gfs20090907162501123.grb";
public GribPlugin() throws IOException,
NoValidGribException, NotSupportedException{
ucar.unidata.io.RandomAccessFile gribfile = new
ucar.unidata.io.RandomAccessFile(testfile, "rw");
type = file.getEdition(gribfile);
System.out.println("File read in: " + testfile + ",
Type of Grib File is " + type);
fileDump = new String[3];
fileDump[0] = "gfs20090907162501123.grb";
fileDump[1] = "gribdump.out";
fileDump[2] = "true";
try{
gridSection = new
Grib1GridDefinitionSection(gribfile);
System.out.println("defining a new gridsection");
}
catch(IOException e){
throw new IOException("Grid Section " + e);
}
System.out.println("grid definition section");
System.out.println("dx: " + gridSection.getDx() + ",
dy: " + gridSection.getDy() + ", La1: " +
gridSection.getLa1() + ", La2: " +
gridSection.getLa2() + ", Lo1: " +
gridSection.getLo1() + ", Lo2: " +
gridSection.getLo2() + ", Nx: " + gridSection.getNx()
+ ", Ny: " + gridSection.getNy() + ", Grid Section
Name: " + gridSection.getName());
System.out.println("File Dump Information");
gribDump.main(fileDump);
System.out.println("Dump GridFile Info Out To File");
ps = new java.io.PrintStream("grib.out");
index = gribIndex.writeFileIndex(gribfile, ps, true);
//this is printing out the grib records
System.out.println("Grib Records");
gribRecords = index.getGribRecords();
System.out.println("Number of Grib Records: " +
gribRecords.size());
for(int i = 0; i < gribRecords.size(); i++){
System.out.println(gribRecords.get(i).category + " " +
gribRecords.get(i).center + " " +
gribRecords.get(i).discipline + " " +
gribRecords.get(i).paramNumber + " " + <--how
do you convert this to the equivalent param name??
gribRecords.get(i).productType + " " +
gribRecords.get(i).decimalScale + " " +
gribRecords.get(i).gdsKey + " " +
gribRecords.get(i).typeGenProcess + " " +
gribRecords.get(i).forecastTime + " " +
gribRecords.get(i).refTime + " " +
gribRecords.get(i).subCenter + " " +
gribRecords.get(i).bmsExists);
} //end for
} //end public class constructor
} // end class GribPlugin
Console Output:
File read in: gfs20090907162501123.grb, Type of Grib
File is 1
GribPDSLevel: Table 3 level 96 is not implemented yet
PDS: Time Unit 9 is not yet supported
Using default table:resources/grib/tables/wmo_2_v1.tab
(0:0:-1)
defining a new gridsection
Grid 28 not configured yet
grid definition section
dx: 2.632, dy: 0.0, La1: -8355.851, La2: 591.622, Lo1:
65.536, Lo2: 0.256, Nx: 540, Ny: 24583, Grid Section
Name: Latitude/Longitude Grid
File Dump Information
gds exception was caught
Dump GridFile Info Out To File
Grib Records
Number of Grib Records: 3
-1 7 0 11 10 1 2350466037 96 24 2009-09-07T06:00:00Z 0
false
-1 7 0 11 10 1 2350466037 96 48 2009-09-07T06:00:00Z 0
false
-1 7 0 11 10 1 2350466037 96 72 2009-09-07T06:00:00Z 0
false
*****
Now you will notice that my grid definition section
does not match any of the parameters from the grid
dump below(except for the grid section name). My
question is, is why is this and/or what am i doing
wrong here??? Those numbers that i get from the
Console output just do not make any sense to me at
all.
*****
GridDump Output:
Header : GRIB1
Discipline : 0 Meteorological
Products
GRIB Edition : 1
GRIB length : 354
Originating Center : 7 US National Weather
Service (NCEP)
Originating Sub-Center : 0 WMO Secretariat
Product Definition : 10 product valid at
reference time P1
Parameter Category : -1 Meteorological
Parameters
Parameter Name : 11 TMP Temperature
Parameter Units : K
Reference Time : 2009-09-07T06:00:00Z
Time Units : hour
Time Range Indicator : product valid at RT + P1
Time 1 (P1) : 24
Time 2 (P2) : 0
Generating Process Type : 96 Global Forecast
System Model (formerly known as the Aviation)
Level Type : 1 surface
Level Value 1 : 0.0
Level Value 2 : 0.0
GDS Exists : true
BMS Exists : false
Number of data points : 3447
Grid Name : Latitude/Longitude Grid
Grid Shape: 0 spherical
Spherical earth radius: 6367.47
Nx : 16
Ny : 15
La1 : 0.0
Lo1 : -100.0
Resolution & Component flags : 128
Winds : True
La2 : 29.0
Lo2 : -70.0
=============================================================================
==
Robb Kambic Unidata Program Center
Software Engineer III Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx WWW: http://www.unidata.ucar.edu/
=============================================================================
==
===============================================================================
Robb Kambic Unidata Program Center
Software Engineer III Univ. Corp for Atmospheric Research
rkambic@xxxxxxxxxxxxxxxx WWW: http://www.unidata.ucar.edu/
===============================================================================
