Re: [cf-pointobsconvention] Draft 2

Dear John

>   3. z coordinate required, with values in any vertical coordinate system.
>   4. z coordinate required, may be a "nominal" value (just a string 
description)
>   5. No z coordinate required.
> > I would lean towards 4, but could be convinced of 5 or 3. We > should however recommend the data provider add as much info as > possible, and make sure there is a standard way to do so.

I think it should be 5, but if there is a Z value, it should be 3.
In the atmosphere, raobs measure pressure and it is converted to
height so the "real" z coordinate is not convertible to meters.
And as I mentioned earlier, if you require 1 or 2, you cannot store
satellite derived winds in that format because you have no height value.

... if there is no Z value,
what do I do if you go with 4?  Just have a string called "unknown"?

I agree with these arguments of Don's. Also, in a case where the data is on a
"special" level which can only be named, rather than given a numerical z-coord,
that should be indicated by the standard name (though I note John Graybeal's
reservation about this, which is that the same instrument might be producing
data of different stdnames when used for different purposes).

I agree with you, of course, that if the z-coord exists meaningfully it should
be provided, to make the data more useful. However, our usual kind of policy in
CF would be to make this a recommendation, rather than a requirement. There is
lots of optional metadata that good practice would include when relevant. Too
many *requirements* are a deterrent to adoption of the standard.

Best wishes

Jonathan