Hi Steve -
Are all the terms in the new vocabulary backwards compatible, other
than non-ASCII characters and log units?
I just spent some time looking on the unidata web site to see if I could
find any information on changes to basic units names - additions or
otherwise. I'd thought there might be some new basic units, e.g. PSU
for salinity. There doesn't seem to be any way to compare the two
versions, as they're in very different formats. (The new xml list is
great, by the way.)
Lots of people and systems, including the CF spec, use the vocabulary
for basic units from udunits, so when and if these terms change, it would
be helpful to have a description of those changes. The v2 manual doesn't
mention any additions, other than new support for non-ASCII and log
units.
In 10/2006, Alison wrote:
It emerged that there are already some units that have been identified as being
useful for CF that are not currently part of udunits.
Jonathan wrote:
> sverdrup = 1e6 m3 s-1 (we can't use the usual abbrev Sv though as it
> already has another definition)
> PSU and psu = 1e-3 (practical salinity unit, effectively mass
> fraction)
There is also decibel (dB).
Thanks -
Nan Galbraith
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 >
...
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.
...
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
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