Dear Mark Thanks for your posting. I prefer the second option
> 2. expanded syntax for grid_mapping attribute on a data variable > - grid_mapping = "Easting:Northing:Height:OSGB Lat:Lon:geogHeight:GeogCS" Although parsers should be tolerant about this, it would be more like other such CF atts if it were a blank-separated list i.e. spaces after ":" Also I would suggest that if it was like this instead "OSGB: Easting Northing Height GeogCS: Lat Lon geogHeight" i.e. GRID_MAPPING_VAR: COORD_VAR [COORD_VAR ...] [GRID_MAPPING_VAR: ...] it would be more like the existing format of the grid_mapping att, which is just "GRID_MAPPING_VAR". It would be immediately obvious which format was being used because in the new format the first word ends in : and there are several words. If the software didn't know about the new format, and interpreted the string in the old format, it would give an error because it would find the grid_mapping variable named does not exist. That would be safe. It is also more backward-compatible because we still have the grid_mapping att on the data variable, and thus we continue to link the coordinates and grid_mappings var via the data variable. This is the consistent with the general way CF works, that the data variable is the main point of reference, which links to the metadata in various ways. Actually I am unclear, in this particular example, why we do need two grid_mapping atts. Wouldn't a single one be sufficient to describe the Mercator projection and the figure of the Earth, and thus the relationship between the lat-lon and the Mercator projection x-y coords? I'd probably understand better if you could illustrate this with a CDL example. Best wishes Jonathan _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
