Hi Jonathan,
This sounds like a good proposal to me.
Brian
On Sat, Dec 23, 2006 at 10:17:32PM +0000, Jonathan Gregory wrote:
> Dear all
>
> This debate went quiet about a month ago. I'd like to propose the following,
> in the light of what was said then.
>
> Requirement: A way to identify the horizontal coordinate variables.
>
> (NB coordinate variables means 1D, in the Unidata sense, as usual in CF.)
>
> Proposal: It can be done using COARDS rules for units in the case of latitude
> and longitude. In other cases (such as projection coordinates, rotated latitude
> and longitude) the standard name can be used, but that requires recognising
> specific names, and standard names are optional anyway. The axis attribute is
> also optional but if present it can be used to identify horizontal coordinates
> as those having axis="X" or axis="Y". If both X- and Y-axis are identified,
> X-Y-up should define a right-handed coordinate system i.e. rotation from the
> positive X direction to the positive Y direction is anticlockwise if viewed
> from above. The axis attribute is allowed for longitude (X) and latitude (Y)
> coordinate variables. The axis attribute is not allowed for auxiliary
> coordinate variables. Auxiliary coordinate variables can be identified as
> lying in the horizontal surface (e.g. 2D latitude and longitude) by the fact
> of their having dimensions which all belong to 1D horizontal coordinate
> variables.
>
> Change to current standard: Remove the prohibition on axis attribute for
> rotated lat and lon. Introduce the requirement for X-Y-up to be right-handed.
> Add a remark about how aux coord vars can be inferred to be horizontal. Make
> it clear that axis is not allowed on aux coord vars (but that is probably
> already the case, so not a change to the standard).
>
> Cheers
>
> Jonathan
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://www.cgd.ucar.edu/mailman/listinfo/cf-metadata
Received on Sun Dec 24 2006 - 15:39:00 GMT
