[CF-metadata] [UDUNITS #UVU-592022]: information

From: Unidata UDUNITS Support <support-udunits>
Date: Wed, 07 Apr 2010 11:24:34 -0600

Christina,

> Sorry for the delay in this new question...(I was ill!).

I hope you're feeling better.

> If you use udunits2 you can find what follows:
>
> udunits2: Using default XML database
> You have: 1mg
> You want: kg
> 1 mg = 1e-06 kg
> x/kg = 1e-06*(x/mg)
> You have: milligrams
> You want: kg
> 1 milligrams = 1e-06 kg
> x/kg = 1e-06*(x/milligrams)
> You have: microkg
> You want: kg
> 1 microkg = 1e-06 kg
> x/kg = 1e-06*(x/microkg)
>
> In a previous email you suggested me not to use "microkg" and to use
> "milligram"......but....."mg" is wildspread used as it is shorter than
> "milligram" and it seems to me that is recognized by udunits as
> well.....
>
> Why should we prefer "milligram"?

You should favour "milligram" over "mg" because the former is understood by more people than the latter. Yes, the UDUNITS package understands both, but netCDF files are also printed-out sometimes by utilities like ncdump(1). Also, people sometimes use odd abbreviations (e.g. "mcg" for microgram), so using the fully-spelled-out name is a good habit to adopt to prevent you from using an abbreviation that is common in your field but not so common elsewhere.

> thanks in advanced
>
> Sorry for all these doubts, but we are trying to harmonize Ocean color
> data produced by 5 different production centers.Nobody would want to
> change anything......they are currently use "mg m-3" for chloropyll
> and wnat to know why the should now use "milligram".

If they're already using "mg m-3", then they don't have to change: those symbols are ISO-compliant. I recommend that future usage favour fully-spelled-out names, however, when possible.

> BUT WE NEED TO BE COMPLIANT WITH CF SPECIFICATION...AND SO....WE MUST
> BE SURE TO USE A UNITS RECOGNIZE BY UDUNIT.....

The UDUNITS package understands all ISO unit specifications.

As far as I know, the CF members have not yet decided to recommend fully-spelled-out units. That's something that I recommend.

> LET ME KNOW!
>
> SINCERERLY
>
> CRISTINA
>
> -------------------------------------------------------------------
> Cristina Tronconi
> Istituto di Scienze dell'Atmosfera e del Clima - sezione di Roma
> Consiglio Nazionale delle Ricerche
> Via Fosso del Cavaliere 100
> 00133 Roma, Italy
> Tel: +39 06 49934342
> cell: '39 349 1242954
> Fax: +39 06 20660291
> e-mail: cristina.tronconi at artov.isac.cnr.it

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: UVU-592022
Department: Support UDUNITS
Priority: Normal
Status: Closed
Received on Wed Apr 07 2010 - 11:24:34 BST