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[netCDF #ERT-660455]: Unable to retrieve an attribute from a variable using the netcdf C library

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  • Subject: [netCDF #ERT-660455]: Unable to retrieve an attribute from a variable using the netcdf C library
  • Date: Tue, 24 Apr 2012 14:35:51 -0600
Hi Magali,

> Two variables in a netcdf file that I am parsing are described like this :
> 
> double lon_rho(eta_rho=288, xi_rho=263);
> :long_name = "longitude of RHO-points";
> :units = "degree_east";
> :_CoordinateAxisType = "Lon";
> double lat_rho(eta_rho=288, xi_rho=263);
> :long_name = "latitude of RHO-points";
> :units = "degree_north";
> :_CoordinateAxisType = "Lat";
> 
> 
> I'm trying to retrieve the value of the attribute "_CoordinateAxisType" of
> this variable, but it does not work.
> I'm using the 4.1 C version of the library.
> 
> Does the version 4.2 permits to do that ? Or is this not possible to do so
> using the C library, as I saw that it was recognized in the Java library ?

The "_CoordinateAxisType" variable attribute is not a real attribute
in the data file, it's a "virtual" or "synthesized" attribute that's
created by the Java software as it's reading and analyzing the
metadata.  The netCDF C software doesn't see the attribute and doesn't
create it from the metadata, even in version 4.2.

Is there a good reason you need this attribute?  If you are reading the
data and metadata with software that follows the CF metadata
conventions, it will know that lon_rho and lat_rho are longitude and
latitude coordinates, because the units attributes are what CF expects
to specify those coordinate axes.

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                      http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: ERT-660455
Department: Support netCDF
Priority: Normal
Status: Closed