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#107: CF Data Model 1.7 -----------------------------+---------------------------------------------- Reporter: markh | Owner: [email protected] Type: task | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by davidhassell): Replying to [comment:19 markh]: Dear Mark, > Replying to [comment:18 davidhassell]: > > > So, transform_crsOSGB defines a mapping from coordinates '''x''' and '''y''' to latitude-longitude coordinates on a particularly shaped earth; and transform_crsWGS84 defines a mapping from coordinates '''lat''' and '''lon''' to latitude-longitude coordinates on a different particularly shaped earth. > > crsOSGB and crsWGS84 do a lot more than define a transform. They define a coordinate reference system that coordinates are defined with respect to. This is fundamental and far more powerful than defining a transformation, it provides a well recognised definition of what the coordinate means. The way I see it, the purpose of a coordinate construct is to geo-locate the data. If it contains enough metadata for its array values to do this, then that is fine. If not then a transform construct provides the extra information needed by the coordinate construct to do that geo-location. Is this different to your coordinate reference system? Perhaps the name "transform construct" is troublesome. If I recall correctly (?), we chose it because its practical purpose in the conventions is to record how one set of coordinates may be ''transformed'' into another set of (possibly more meaningful) coordinates. Note that whether the latter set exists, or not, is immaterial to the data model, as is the domain of the transformation (horizontal (grid_mapping), vertical (formula_terms), or anything else). All the best, David -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/107#comment:20> CF Metadata <http://cf-pcmdi.llnl.gov/> CF Metadata This message came from the CF Trac system. To unsubscribe, without unsubscribing to the regular cf-metadata list, send a message to "[email protected]" with "unsubscribe cf-metadata" in the body of your message.
