Dear Randy
I agree with what you write. You could list the alternative sets of three
coordinates each all as auxiliary coord vars, and distinguish them with
standard_names; presumably you would want to propose some new standard_names.
That would be fine and quite simple to do.
In addition, you could propose new grid_mappings. Up to now grid_mappings
have been for 2D coordinate systems, but you would want something in 3D,
I think. If it's likely generally useful, it would interesting to see a
proposal of what it might look like.
There is already an agreed change to the CF standard to allow more than
one grid_mapping for a given data variable. This was proposed by Mark Hedley
in ticket 70
https://cf-pcmdi.llnl.gov/trac/ticket/70 and will go in CF 1.7.
In response to Jim's comment, I would say that the data variable does have a
coordinate system; it's defined by the various coordinate variables that the
data variable is associated with, either 1D (Unidata) coordinate variables
or auxiliary coordinate variables. The role of the grid_mapping is to make
explicit the relationship among the coordinate variables of the space in which
the data variable exists.
Best wishes
Jonathan
Received on Wed Sep 05 2012 - 11:28:28 BST
