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On Wed, 31 Oct 2007, Ben Domenico wrote:
Hi Gerry, As you are no doubt aware, that issue has to be addressed on multiple fronts. -- The ISO 19123 definitions are general enough to support such datasets as coverages. -- The WCS specifications have been more restrictive to the point where the grids must be regular in some (perhaps) projected coordinate system. -- The CF conventions community has, to this point, focused on the regular (or at least quasi regular) grids that are the output of numerical forecast models.
irregular grids still needs some work. If we can complete the process for the case of "station observations," I believe the others will follow more quickly by benefit of the hard lessons we are learning from the first two. One question I have for you and the other members of the coastal community is whether those unstructured/irregular grids are an example of one of the current CDM scientific data types http://www.unidata.ucar.edu/projects/THREDDS/CDM/CDM-TDS.htm or whether a new CDM data type is needed.
From that document, the Station (or perhaps Swath?) type seems like theclosest CDM Scientific Data Type to the elements in an unstructured grid model. However there does not seem to be a clear method to limit the domain of applicability of a Station's data to some non-simple spatial region associated with a CDM Station. Unstructured mesh modelers use nodes and a connectivity matrix to represent the regions over which their data applies, and are writing these in netCDF outside of the conventions.
Maybe a 'Cell' or 'Element' data type using nodes/vertices and some sort of connectivity would be a valuable extention.
Dave -- Dr. David Forrest drf@xxxxxxxx (804)684-7900w drf5n@xxxxxxxxxxxxx (804)642-0662h http://maplepark.com/~drf5n/