On 07-01-15 17:10, Steve Emmerson wrote:
> Jonathan,
>
> I think you meant to say that if a physical quantity has a different
> dimensionality (not unit), then we have to give it a different name.
>
> In my opinion, what's needed in this case is a package that understands
> co-ordinate transformations -- in order to convert, for example, values
> in units of "1e15/cm2" to values in units of "mol/m2". This is a rather
> simple example and Maarten makes a good (though not yet convincing to
> me) argument for simply modifying the UDUNITS database. One can imagine,
> however, more complicated cases in which simple unit conversions are not
> possible (e.g., converting between altitude and pressure). Such a
> package would be easily capable of handling Maarten's conversion.
The only argument I'm making is that 'molecules' is available as a unit
equivalent to 'avogadros_number-1' (which is the case with the current
release of UDUnits). People who use 1/cm2 when they (implicitly) mean
molecules/cm2 get what they deserve IMHO.
As soon as you have molecules/cm2, then UDUnits can handle the
conversion as is. For other densities, say an aerosol particle count,
the conversion to mol is never needed, and number densities are fine
(and a look at the standard_names will confirm this).
So right now I'm not asking anything, as the most important scaled alias
for 'mol' is available. This will ease the transition to mol/m2 quite
significantly. It would be good to help the transition from photons to
mol (photons) as well, which was a request that started this whole
discussion in the first place.
Does this make the argument clearer?
Best,
Maarten Sneep
--
KNMI
T: 030 2206747
E: maarten.sneep at knmi.nl
R: A2.14
Received on Wed Jan 07 2015 - 10:31:02 GMT
