[netcdf-java] Questions about handling dimensionless coordinates


I'd like to add support for dimensionless vertical coordinates in ncWMS and I 
have a few questions:

1.       How common is it for the transformation between dimensionless coords 
and natural coords to be time-dependent?  Under what circumstances would this 
occur?  Does it happen when the coordinate depends on a pressure field that 
varies with time?

2.       If the VerticalTransform exists, can I assume that 
getCoordinateArray() will always return a valid array, i.e. that nj4 has 
automatically found all the auxiliary fields necessary to create the transform 
(such as pressure)?

3.       I can see how to get the units of the transformed vertical coordinate 
(i.e. the "natural" coords, via VerticalTransform.getUnitString()) but how can 
I get the "positive" direction?  In other words, if the natural coordinates are 
in metres, how do I know whether this is depth or height?

4.       What would be the most "natural" interpolation method in the vertical 
when transforming a gridded field from dimensionless coordinates into levels - 
nearest-neighbour or linear?  (Or something else?)


Dr Jon Blower
Technical Director, Reading e-Science Centre
Environmental Systems Science Centre
University of Reading, UK
Tel: +44 (0)118 378 5213

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