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