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On 5/4/2011 9:51 AM, Jon Blower wrote:
Hi,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?
yes, thats the common case that ive seen: surface_pressure(time) for hybrid/sigma coordinates. Im not sure about the ocean vertical coordinates.
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)?
yes, it will fail fast (at construction) if theres a problem.
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?
hmm, i never thought of that problem. im guessing a domain expert could look at these:
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/cf-conventions.html#dimensionless-v-coord and tell us the right answer, which we could then embed into the code.
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?)
dunno - id guess linear or log, depending on the transform. perhaps the domain expert could look at the above list and give some advice.
Thanks, Jon -- Dr Jon Blower Technical Director, Reading e-Science Centre Environmental Systems Science Centre University of Reading, UK Tel: +44 (0)118 378 5213 http://www.resc.reading.ac.uk <http://www.resc.reading.ac.uk/> _______________________________________________ netcdf-java mailing list netcdf-java@xxxxxxxxxxxxxxxx For list information or to unsubscribe, visit: http://www.unidata.ucar.edu/mailing_lists/
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