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Re: [cf-pointobsconvention] Draft 2

I think 'requiring a Z' and 'requiring a Z with every point' are two different things. I don't think anyone meant to argue for the latter, or they'll correct me if I'm wrong.
To take an easy case first, for surface-based measurements like ship point observations, specifying 'surface' in one place for all Z coordinates (e.g., via an attribute) seems like a reasonable approach. Hurricane track (great example) may be a little more complex -- I don't know if the science would say that is a 'surface' value, or something less concrete. But it would be OK with me to allow the attribute to take on a value representing an abstraction, if that's necessary. 

John

At 11:31 AM -0600 9/18/07, Don Murray wrote:

John Caron wrote:

John Graybeal wrote:
Re the Z axis, it would be nice to know for sure whether the Z axis
should be interpreted as 'surface'.  (Other possible surfaces
exist, and I suppose an abstract form of Z is also possible.  So if
we want determinism, we could either say "lack of characterization
always means surface" or "Z must be described, if only to say it is
'surface'.")


Yes, after thinking more about it, Im not so sure we should allow
data that doesnt have a z coordinate. A standard I think should be
allowed to insist on things like this.


Then what do you do with a hurricane track that does not have
an z associated with it?  Or a trajectory from ship point obs
that only have a latitude/longitude?  It seems like wasted
space to have to write out 0 for z for every point if you don't
have it and there are plenty of datasets out there without a
Z value.


--
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John Graybeal   <mailto:graybeal@xxxxxxxxx>  -- 831-775-1956
Monterey Bay Aquarium Research Institute
Marine Metadata Initiative: http://marinemetadata.org || Shore Side Data System: http://www.mbari.org/ssds