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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 markh): Replying to [comment:52 biard]: > Isn't it true that, as it currently stands in CF, coordinates do not reference any coordinate systems? I think it would be superior to have the coordinates directly reference their coordinate systems, but I think that in the current arrangement, a data variable declares an association between coordinate variables and CRSs via the grid_mapping attribute (either implicitly or explicitly, depending on the syntax chosen). Hello Jim In CF 1.6 this appears to be the case. However, there are a number of implications that the coordinate variables which are the `Axis=='X'` and `Axis=='Y'` coordinates are defined with respect to this coordiante reference system. In order to make this implication more explicit and support multiple coordinate reference systems within the scope of a data variable, the ticket #70 was raised, discussed and is now approved. This will appear in CF 1.7. This ticket makes it explicit that the semantics of all grid_mapping relationships are of coordinates defined with respect to coordinate reference systems. The association is controlled by the data variable and the syntax is defined to maintain backwards compatibility but the semantics are explicit: each coordinate is defined with respect to one coordinate reference system or None. The fact that the declaration is made by the data variable is an encoding detail, not key semantic information. By keeping the backwards compatibility we firm up the interpretation of all grid_mapping attributes on data variables and maintain consistency for both syntax options. Are you content that this interpretation provides your ''superior approach'': that ''coordinates directly reference their coordinate systems''? mark -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/107#comment:53> 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.
