Andrew, > I'm running into some problems regarding units in CF-compliant files. > Up until now I've been using udunits 1 to check units, but I recently > tried the CF checker which uses udunits2. There are some unit strings > which are valid in one but not the other. In particular, I am dealing > with milligrams per cubic meter. In udunits1, I used 'ukg m-3', which > udunits2 rejects as invalid. udunits2 accepts 'mg m-3' (which is much > better!), but udunits1 interprets this as to do with gravity. Because > of this, I can't include a unit string which is generally compatible > with udunits...
> I would guess that udunits2 is the preferred option, given that > udunits1 is deprecated. Should the CF conventions be updated to > specify udunits 2? The UDUNITS-1 library had a bug in it. The bug was that "g" was interpreted as meaning "gravity" (i.e., "standard_free_fall") rather than "gram". This was corrected in version 1.12.10 of the UDUNITS-1 package, which was released on 2009-09-17. The UDUNITS-2 package did not have this bug from the outset. If you create a CF file that uses "g" for "gram", then it will be correctly interpreted by the UDUNITS-2 library and also by the UDUNITS-1 library from version 1.12.10 on. Applications that use the UDUNITS-1 library prior to version 1.12.10 can be easily modified to interpret "g" as "gram" by removing the following entry from the UDUNITS-1 database ($prefix/etc/udunits.dat): g S gravity # approx. should ... I hope this helps. Regards, Steve Emmerson UDUNITS developer _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
