[CF-metadata] Coordinate System nomenclature in netcdf-java-2.2 / CDM:

From: John Caron <caron>
Date: Wed, 22 Dec 2004 14:23:11 -0800

Brian Eaton wrote:

>On Wed, Dec 22, 2004 at 02:28:16PM -0500, Rich Signell wrote:
>
>
>>This seems to be agreeing with Brian's earlier statement that saving 4D
>>fields of Z are allowed already, enabled by the "coordinates"
>>attribute. Can one of you guys give an example of how this would be
>>done? I have only seen the "coordinates" attribute used to specify
>>two-dimensional longitude and latitude fields.
>>
>>
>
>In general, the "coordinates" attribute is used to point to variables that
>contain coordinate information that can't be represented by a coordinate
>variable (note that the conventions always use the term coordinate variable
>to mean a 1D variable whose name matches the name of its dimension). The
>only restriction on an auxiliary coordinate variable are that its
>dimensions are a subset (not necesarily proper) of the variable to which it
>is attached (and of course there's an exceptional case for dealing with
>label coordinates).
>
FYI, we have started using the following nomenclature in the Coordinate
System layer in netcdf-java -2.2 and the common data model:

A "coordinate variable alias" is really a coordinate variable (1D,
monotonic) but its name doesnt match its dimension.

A "coordinate axis" is a generalization of a coordinate variable, it may
have more than 1 dimension and may have any name. it acts like a
coordinate variable in that it assignes a coordinate value to each value
in a data variable. It is the same i think as CF's "auxiliary coordinate
variable". A coordinate variable is also a coordinate axis.

A "coordinate system" for a data variable is a set of coordinate axes.

A "georeferencing coordinate system" for a data variable is a set of
coordinate axes that give us lat, lon (or x, y on projection plane), z,
and time coordinates for each value in the data variable.
Received on Wed Dec 22 2004 - 15:23:11 GMT