Dear Sean, Robert,
Thanks to both for the fast reply.
I’ve sent you a link to the sample NetCDF4 files, generated with Python’s
netCDF4 package (custom code)
and GDAL v1.11 utilities.
I’ve tried several options (like datatype for dataset or valid_range, _Unsigned
attribute, etc), as you
can see in the four examples (prefixed 1_, 2_,… in filename).
H5dump –A output for each file is included as well (h5d_1.txt for the file
1_...nc and so on).
Files 1-2-3 use signed integer datatype:
· dataset LAI cannot be shown on standard geo2D plot in Panoply
· CF compliance checker at Reading, UK gives no warning or error (and I
know it checks datatypes),
so file is (largely) compliant with CF v1.6.
File 4 uses unsigned datatype
· can be read/plotted in Panoply, though the valid range is printed
wrongly (0…-46 but UB type)
· CF compliance checker complains
ERROR (8.1): LAI must be of type byte, short or int
and section 8.1 of CF conventions doc mentions the use of signed integers.
The LAI-QFLAG 16-bit dataset is shown properly though, so I think you can focus
on LAI dataset
and possibly byte/ubyte for the tests.
Best regards,
Tim
From: Sean Arms [mailto:sarms@xxxxxxxx]
Sent: woensdag 25 november 2015 18:38
To: Jacobs Tim
Cc: netcdf-java@xxxxxxxxxxxxxxxx
Subject: Re: [netcdf-java] NetCDF-Java CF compliance
Greeings Tim,
Good question. Typically users have a issues with netcdf-java and unsigned
ints, as Java does not have an unsigned int primitive type. However,
netcdf-java fully supports signed ints. For a list of supported datatypes,
checkout:
http://www.unidata.ucar.edu/software/thredds/v4.6/netcdf-java/CDM/DataType.html
It looks like the latest version of panoply is using the latest release of
netcdf-java (v4.6.3), so I do not see anything on the netcdf-java side that
could be an issue. netCDF-3 only uses signed types, so one quick way to check
panoply is to open a netcdf-3 from from a different dataset or source and see
if you can view any int fields.
I'd be more than happy to take a look at your specific file to see if anything
jumps out to me on the netcdf-java side.
Cheers,
Sean
On Wed, Nov 25, 2015 at 1:18 AM, Jacobs Tim
<tim.jacobs@xxxxxxx<mailto:tim.jacobs@xxxxxxx>> wrote:
Dear Unidata colleagues,
CF conventions are more restrictive than NetCDF regarding
the data type used for the variables. CF for instance requires the use
of signed integers. However, NASA’s Panoply, that uses NetCDF-java,
cannot display variables with signed integer datatype, whereas changing
to unsigned equivalent works fine.
Can NetCDF be updated to accommodate also signed integers?
Or is the problem in Panoply’s own code?
Best regards,
Tim Jacobs
Remote Sensing Dept.
VITO NV
Boeretang 200
2400 Mol
Belgium
Tel: +32 14 336710<tel:%2B32%2014%20336710>
Skype: jacobs.timmeke
VITO Disclaimer: http://www.vito.be/e-maildisclaimer
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