Do you really need an attribute here? Can you construct a scenario in which increasing values consistently represent a _lesser_ pressure/depth of water?
Since the variable really is representing pressure, not depth of water, I think it's safe to say that increasing values of course represent increasing pressure. If that's fair, then adding the positive attribute raises questions rather than resolving them.
John
On Jul 18, 2011, at 02:42, Comiskey, Glenn wrote:
> Hi,
>
> The COARDS covention mandates the use of the "positive" attribute for a vertical axis that is not a unit of pressure, i.e. if using metres to denote altitude. It further qualifies use of the "positive" attribute as a means of discovering vertical coordinate variables, i.e. the convention states "A vertical coordinate variable will be identifiable by: units of pressure; or the presence of the positive attribute..." Does this, therefore, restrict use of the "positive" attribute to vertical coordinate variables only? NOTE: CF convention (v1.5, Appendix A: Attributes, page 50) reports use of the "positive" attribute as relating to coordinate data only.
>
> I ask as I have a number of datasets in which the vertical coordinate variable is present, named "altitude" albeit it represents sea level with a value of 0 (zero), unit value of metres and has a declared "positive" attribute of "up", but also contains tidal data reporting the height of the water column above a pressure gauge and an attribute is wanted to be added to denote that increasing values represent a greater depth of water, i.e. "positive" is down. Would use of the "positive" attribute for data variables interfere with the discovery of vertical coordinates as defined by COARDS?
>
> Kind regards,
>
> Glenn Comiskey
> Data System Administrator
>
> Fugro Global Environment & Ocean Sciences
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John Graybeal <mailto:jgraybeal at ucsd.edu>
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Ocean Observatories Initiative Cyberinfrastructure Project:
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Marine Metadata Interoperability Project:
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