It has been added to CF, but because of an oversight, hasnt been
published yet. Follow the specs on this page:
http://cf-pcmdi.llnl.gov/trac/wiki/GridMapNames
Don Murray wrote:
> Hi Eric-
>
> Kemp, Eric M. (TASCSD) wrote:
>> I am writing a post-processor for the WRF model. My intent is to
>> generate new netCDF files with optional derived variables on pressure
>> surfaces. I have been writing my code to use the CF-1.0 convention
>> as recommended in the IDV documentation, but this week I discovered
>> that the CF convention does not include the Mercator map projection.
>> (Note that the Transverse Mercator projection included in CF
>> is not the same projection.)
>
> We have proposed Mercator as a standard for CF, but it has not been
> accepted yet. However, you can define it as:
>
> mercator
>
> char Mercator_Projection;
> :grid_mapping_name = "mercator";
> :longitude_of_projection_origin = 110.0;
> :latitude_of_projection_origin = -25.0;
> :standard_parallel = 0.02;
> :_CoordinateTransformType = "Projection";
> :_CoordinateAxisTypes = "GeoX GeoY";
>
> See the reference at:
>
> https://www.unidata.ucar.edu/software/netcdf-java/reference/StandardCoordinateTransforms.html
>
>> I've made two attempts to work around this while remaining in the
>> CF convention: (1) label the data as Lambert Conformal with the
>> standard latitudes equidistant from the equator, which is supposed
>> to be equivalent to the Mercator projection; and (2) not write out
>> any grid_mapping metadata, but include the latitudes/longitudes at
>> each grid point. In the first case, IDV freezes up and has to be
>> killed. In the second case, IDV claims there are no gridded data
>> in the file, even though the data meets the CF convention (the
>> grid_mapping metadata is listed as optional in the CF documentation).
>
> Can you provide sample files so we can look into this?
>
>> So at this point, I'm looking for help on how to encode this for
>> IDV. One extreme possibility is to abandon the CF convention and try
>> using the _Coordinate convention described in the NetCDF-Java
>> documentation, but I'd appreciate feedback before taking such a
>> drastic step.
>
> Try using the definition above.
>
>> (Note that my post-processor should also support other map projections
>> used by WRF, so I'd like the output convention to be as flexible
>> as possible.)
>
> Don
> *************************************************************
> Don Murray UCAR Unidata Program
> dmurray@xxxxxxxxxxxxxxxx P.O. Box 3000
> (303) 497-8628 Boulder, CO 80307
> http://www.unidata.ucar.edu/staff/donm
> *************************************************************
>
> _______________________________________________
> idvusers mailing list
> idvusers@xxxxxxxxxxxxxxxx
> For list information, to unsubscribe, visit:
> http://www.unidata.ucar.edu/mailing_lists/
