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#104: Clarify the interpretation of scalar coordinate variables -----------------------------+---------------------------------------------- Reporter: jonathan | Owner: [email protected] Type: enhancement | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by caron): Hi Jonathan: This representation: {{{ variables: float lat; float lon; float time(time); float temp(time); temp:coordinates="lat lon"; }}} would be interpreted as having three independent dimensions. But thats incorrect, or at least should be optional. It should be possible to interpret this as having only one independent coordinate, ie "1D". But theres no way to represent that in proposal #104. The more general issue is that the number of dimensions and the number of coordinates have different meanings. Interpreting a scalar coordinate as a dimension 1 coordinate (meaning independent) complicates things without any gain that i can see. Better is to let it be understood as a dependent variable, and if you want to indicate that its an independent coordinate, then you have to make it a coordinate variable, ie give it a dimension of length 1, and add that dimension to the data. OTOH, theres nothing special about a scalar coordinate, and should not be handled in a special way in the data model. Its just an auxiliary coordinate, period. By the current definition of coordinate and auxiliary coordinate, its clearly an auxiliary coordinate. What this discussion has helped clarify for me is that coordinate variables are independent, and auxiliary coordinates are dependent variables. I think thats a really valuable advance in the data model. Things are complicated a bit by the DSG representations that introduce, eg a station dimension, that allows one to factor out the station info from the observation. Since all we have in the classic model are multidimensional arrays, one has to use dimensions for lots of things, not just to indicate the domain dimensionality. I guess we should look hard at the DSG representation to see what it says about the assertion that "coordinate variables are independent, and auxiliary coordinates are dependent variables". regards, John -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/104#comment:58> 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.
