Karl, Jonathan and others,
> I'll reiterate what I said earlier (but I think somehow the email didn't
> get distributed). I'm in favor of eliminating the apparently
> contradictory statements. Of the two choices, perhaps least confusion
> would result from adopting Jonathan's suggestion: restrict X and Y to
> genuine longitude and latitude coordinates.
By 'genuine longitude and latitude coordinates' would you intend to
exclude auxiliary (lat/lon) coordinates (eg lat(y,x) and lon(y,x)), and
allow only for datasets with lat lon dimensions (and hence lat(lat) and
lon(lon) coordinate variables)?
I'm a bit confused since I originally interpreted CF 4 to mean that the
axis attribute as an extra way of identifying a coordinate variable. I
assumed it would be good to use it with auxiliary coordinate variables
for datasets using x,y dimensions and, say, lambert conformal
projection. But then by analogy to the discussion about rotated pole
projections on the earlier part of this thread I got to thinking that
maybe the axis attribute should be associated with the x(x) and y(y)
'projection_x/y_coordinate' variables instead (ie so it can be used as a
hint to the plot orientation).
However, it seems to me that restricting the attribute to only be used
for 'proper' coordinate variables (ie lat(lat), lon(lon)) is a bit
drastic (and it doesn't really add much value to these variables does
it?). All thats really needed is to resolve the ambiguity in intended
usage (ie is it to hint at plot orientation or to help identify
coordinate variables including auxiliary coordinate variables). Of
course if both interpretations are in common use then it gets a bit
trickier...
The reason I was intending to use the axis attribute was just in an
attempt to include as much metadata as possible so that (hopefully) a
wider range of data readers would be able to understand our data; I
guess if its just going to add confusion I won't use it. Does anybody
know of data readers that currently rely on the axis attribute in any way?
regards
Simon
--
Simon Wood
National Institute of Water and Atmospheric Research, Wellington, NZ
simon.wood at niwa.co.nz
http://www.niwa.co.nz
Received on Sun Nov 19 2006 - 19:05:13 GMT
