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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
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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/
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