Problems reading NetCDF data - get NaNs

• To: netcdf-java@xxxxxxxxxxxxxxxx
• Subject: Problems reading NetCDF data - get NaNs
• From: "Jon Blower" <jdb@xxxxxxxxxxxxxxxxxxxx>
• Date: Thu, 19 Oct 2006 09:06:56 +0100

Dear all,

I'm having some problems reading data from a particular NetCDF file.
The code i'm using is:

 NetcdfDataset nc
NetcdfDataset.openDataset("C:\\data\\OA_20060830.nc", true, null);
 GridDataset gd = new GridDataset(nc);
 GeoGrid gg = gd.findGridByName("temperature");
 Array arr = gg.readYXData(0, 0);
 IndexIterator it = arr.getIndexIteratorFast();
 while (it.hasNext()) {
     double val = it.getDoubleNext();
     System.out.println("" + val);
 }
 nc.close();

I just get a load of NaNs, even though I know that there are valid
data in the file (ncBrowse displays the data perfectly).  The only
unusual thing about the data is that the data are stored as short
integers, with an offset and scale factor:

    short temperature(time, depth, latitude, longitude);
       :long_name = "Temperature";
       :missing_value = 32767; // short
       :_FillValue = 32767; // short
       :units = "degree_Celsius";
       :valid_min = -3; // short
       :valid_max = 40; // short
       :add_offset = 20.0; // double
       :scale_factor = 0.0010; // double
       :comment = "Temperature estimate (by objective analysis)";

I understood that the NetcdfDataset class automatically dealt with
offsets and scale factors  in "enhanced" mode, which is what I am
using (or trying to use).  Hence I was expecting to "see" the data as
an array of doubles.  The same happens if I use getFloatNext() or
getShortNext().

Can anyone see what I'm doing wrong?

Thanks in advance,
Jon

--
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Dr Jon Blower              Tel: +44 118 378 5213 (direct line)
Technical Director         Tel: +44 118 378 8741 (ESSC)
Reading e-Science Centre   Fax: +44 118 378 6413
ESSC                       Email: jdb@xxxxxxxxxxxxxxxxxxxx
University of Reading
3 Earley Gate
Reading RG6 6AL, UK
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