[CF-metadata] udunits 1 or 2 for CF?

Andrew Clegg ancl at pml.ac.uk
Wed Mar 3 08:10:43 MST 2010

Hi all,

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 

I would guess that udunits2 is the preferred option, given that udunits1 
is deprecated. Should the CF conventions be updated to specify udunits 2?

Andrew Clegg
Plymouth Marine Laboratory

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