Dear Heiko, > I hope CF could define a default datum, e.g. the GRS1980 > Authalic Sphere, since this matches most closely with > existing software (netcdf-java). This would make live easier > for the software-developers who have to use something if > nothing is given.
I'm not sure that defining a default datum for CF is the right way to go in this instance. I would have thought that if a particular piece of data analysis is at a resolution that requires a geodetic datum to be specified then, in absentia the actual one being defined in metadata, it's not clear to me that using some semi-arbitrary, and potentially invalid, default datum is any better than giving the user the opportunity to select the one s/he believes to be the most appropriate for the task in hand. The current CF conventions include a (fairly minimal) set of metadata attributes which can be used to describe the basic properties of the coordinate reference system associated with a given dataset. The onus then is on data producers to utilise those metadata attributes to describe their data to the fullest extent possible. Furthermore, other non-CF attributes may be used to augment the standard set - over time some of these additional attributes would no doubt find their way into the CF specification. Ultimately, if end-users consider that a given dataset has insufficient metadata to justify its use within a particular context, then they can always choose to ignore that dataset. With the passage of time - and in true Darwinian fashion - such datasets (and their producers) will find that they are increasingly disregarded/overlooked in analyses. Hopefully this would galvanise such data producers into improving the quality of their spatial metadata! Regards, Phil PS: if a default datum were to be encoded into the CF conventions, I'd imagine that the WGS84 datum would be the way to go rather than GRS80 which, if I understand correctly, has somewhat more of a bias towards use over the North American continent. That said, I suspect the differences between the 2 datums are sufficiently small as to get lost in the underflow for many metocean research applications. _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
