Re: [netcdf-java] Rotated latitude/longitude GRIB2 coordinates

  • To: John Caron <jcaron1129@xxxxxxxxx>
  • Subject: Re: [netcdf-java] Rotated latitude/longitude GRIB2 coordinates
  • From: Ben Caradoc-Davies <ben@xxxxxxxxxxxx>
  • Date: Sun, 17 Apr 2016 10:11:27 +1200
On 17/04/16 09:29, John Caron wrote:
The question I never answered for myself  is what is the relationship
between
   ucar.unidata.geoloc.projection.RotatedPole
which was contributed for CF:
[...]
and
   ucar.unidata.geoloc.projection.RotatedLatLon
which was contributed for GRIB data:

John, as far as I can tell (and I added two unit tests to satisfy myself), these two projections produce identical results, and differ only in their projection parameters. Pull request #531 migrated rotated lat/lon GRIB2 support to RotatedPole for conformance with CF Conventions.

The change to use RotatedPole improves interoperability; for example: last week I merged a contributed Rotated_Pole projection into GeoTools (from the COSMO community), and I have support for NetCDF CF Conventions rotated pole in a GeoTools branch (soon to use the new Rotated_Pole projection). The old RotatedLatLon did not conform to CF Conventions and so lacked support.

PS: I presume youve given us some test GRIB files using template 32769
to add to our unit tests?

I have not yet done so. I think that adding a template 32769 file to the Unidata test data set is an excellent idea. I will approach the data owner, seek their permission, and follow up with Christian W-G.

Kind regards,

--
Ben Caradoc-Davies <ben@xxxxxxxxxxxx>
Director
Transient Software Limited <http://transient.nz/>
New Zealand



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