Hello David Thank you for sharing your thoughts. Having considered input from you and Jonathan I think that I am convinced that an extended grid_mapping syntax represents a good approach to meeting the requirements I am aware of.
I guess the next step is to create a trac ticket and propose this extension, with relevant information, such that it can be considered for inclusion in the next revision of the specification. I believe that I can do this fairly soon. Please may someone put themselves forward to moderate this ticket? many thanks mark -----Original Message----- From: [email protected] on behalf of David Hassell Sent: Thu 03/11/2011 10:05 To: [email protected] Subject: Re: [CF-metadata] FW: FW: Connecting coordinates to Grid Mapping variables Hello Mark, Thanks for presenting this clearly. I favour the second option of an expanded syntax for grid_mapping attribute on a data variable. Pragmatically, I think that it is possible for two data variables in the same file to share identical latitude and longitude coordinate values but have different grid_mappings. This would occur, for example, if one data variable came from a climate model which used the spherical earth approximation and the other used a spheroidal earth. In this case, if the coordinate reference information was attached to the coordinates I would need to duplicate the coordinates' data in my file, which is not desirable. > * a view that the coordinate is defined with respect to a coordinate > system and a data variable is defined with respect to a coordinate Conceptually, I prefer a different interpretation of the role of coordinate systems. I like to think of a coordinate reference system as being defined by the arbitrary coordinates which describe the dimensions of a space (or grid) in which a data variable exists. From this view point, hanging space-defining attributes off the data variable seems more natural to me. All the best, David -- David Hassell National Centre for Atmospheric Science (NCAS) Department of Meteorology, University of Reading, Earley Gate, PO Box 243, Reading RG6 6BB, U.K. Tel : 0118 3785613 Fax : 0118 3788316 E-mail: [email protected] _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
