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[netCDFJava #NBT-844482]: problems with add_offset, scale

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  • Subject: [netCDFJava #NBT-844482]: problems with add_offset, scale
  • Date: Tue, 02 Aug 2016 14:17:38 -0600
Heather,

If you're using FileWriter, that only works for netCDF 3. You need to use 
FileWriter2 to get netCDF4:

https://www.unidata.ucar.edu/software/thredds/current/netcdf-java/javadoc/index.html

When you use FileWriter2, you'll also need to pass it 
NetcdfFileWriter.Version.netcdf4 to enable netCDF 4 output with the unsigned 
data types.

For more information about writing files, see this tutorial: 
https://www.unidata.ucar.edu/software/thredds/current/netcdf-java/tutorial/NetcdfWriting.html
Specifically, the last section should be useful.

Ryan

> My default is netcdf 4.  I even had our IT guy go in and make sure that's
> the default for me.  I logged out and back in again to make sure something
> wasn't reset previously, but I still get negative values in the RhoHV
> field.  Do you have any other thoughts on what is going on?
> 
> address@hidden> wrote:
> 
> > Heather,
> >
> > Now that I think about it, the raw data in a Level 2 file are unsigned
> > bytes, so you shouldn't even be able to get a value of -24.
> > If I convert -24 to its unsigned byte equivalent, 232, then the scale and
> > offset give me 0.975.
> >
> > What are you using to read the data back in? Are you converting to a
> > netCDF version 3 file or a version 4 file? The version matters, because
> > netCDF 3 doesn't support unsigned data, so we set an attribute _Unsigned
> > to indicate that the data are unsigned; the data type netcdf variable
> > itself is byte. For netcdf version 4, the data are written as unsigned
> > bytes.
> >
> > Writing out netcdf version 4 files from netcdf-java requires having the
> > netcdf-C library installed and configured, so I'm going to guess you're
> > writing
> > netcdf version 3 files.

Ticket Details
===================
Ticket ID: NBT-844482
Department: Support netCDF Java
Priority: Normal
Status: Closed
===================
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