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Fwd: Problem Reading GRIB Data

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  • Subject: Fwd: Problem Reading GRIB Data
  • Date: Fri, 13 May 2005 14:11:36 +0100
Hello folks,

I was just wondering if anyone in the community has been using the netcdf
library for manipulating GRIB files and if you have come across any problems
related to extracting subsets of data along x-y space of a 4D grid
(T,Z,lat,lon) where size (Z=20,lat=630,lon=899). 

When I am trying to extract it at one go, I am getting the following error
messages:

for range:

              myList.add(0, new Range(0, 0, 1));
              myList.add(1, new Range(0, 9, 2));
              myList.add(2, new Range(500, 550, 1));
              myList.add(3, new Range(700, 725, 1));

              Array arr = myVar.read(myList);
              ArrayList newList = new ArrayList();
 
Error:

java.lang.ArrayIndexOutOfBoundsException: 6630
        at ucar.ma2.ArrayFloat.setFloat(ArrayFloat.java:193)
        at ucar.ma2.IteratorFast.setFloatNext(IteratorFast.java:61)
        at
ucar.nc2.iosp.grib.GribServiceProvider.readXY(GribServiceProvider.java:177)
        at
ucar.nc2.iosp.grib.GribServiceProvider.readLevel(GribServiceProvider.java:150)
        at
ucar.nc2.iosp.grib.GribServiceProvider.readData(GribServiceProvider.java:134)
        at ucar.nc2.NetcdfFile.readData(NetcdfFile.java:848)
        at ucar.nc2.Variable._read(Variable.java:737)
        at ucar.nc2.Variable.read(Variable.java:451)
        at Test2netcdf.readData(Test2netcdf.java:50)
        at Test2netcdf.main(Test2netcdf.java:112)


I have to extract the data in two stages.In the first step, I just have to
extract data at a particular time and depth level(s) but all of
latitude-longitude space.

Then, in second stage I have to apply the range for latitude-longitude.

        ArrayList myList = new ArrayList();
        myList.add(0, new Range(0, 0, 1));
        myList.add(1, new Range(0, 9, 2));
        myList.add(2, new Range(0, 629, 1));//all of lat
        myList.add(3, new Range(0, 899, 1));//all of lon

        Array arr = myVar.read(myList);
        ArrayList newList = new ArrayList();
                
        int[] newShape = arr.getShape();
                                
        newList.add(0, new Range(0, 0, 1));
        newList.add(1, new Range(0, (newShape[1]-1), 1));
        newList.add(2, new Range(500, 550, 1));//apply range for lat
        newList.add(3, new Range(700, 725, 1));//apply range for lon

        Array new_arr = arr.sectionNoReduce(newList);
        float[] data = (float[])new_arr.copyTo1DJavaArray();

This approach is ok  when extracting data from small number of files but the
performance would deteriorate if extracting from 100+ files having quite big
lat-lon spaces. 

Your comments would be much appreciated.

Cheers,

Adit