19950728 Re: Suggested new units for udunits.dat

• To: netcdfgroup@xxxxxxxxxxxxxxxx
• Subject: 19950728 Re: Suggested new units for udunits.dat
• From: Steve Emmerson <steve@xxxxxxxxxxxxxxxx>
• Date: Fri, 28 Jul 1995 13:19:40 -0600

Harvey,

> Subject: Suggested new units for udunits.dat
> To:       netcdfgroup@xxxxxxxxxxxxxxxx
> From: Harvey DAVIES <hld@xxxxxxxxxxxx>
> Keywords: 199507280706.AA11878

In the above message you wrote:
 
> Here are some suggested new units for the units database file 'udunits.dat'.
> 
> CONSTANTS section currently defines 'percent' and '%'.  I suggest also
> ppt                     S 1.0e-3                # parts per thousand
> ppm                     S 1.0e-6                # parts per million
> ppb                     S 1.0e-9                # parts per billion
> ppt                     S 1.0e-12               # parts per trillion

`ppt' in the above is ambiguous.  But I can add `ppm' and `ppb'.
 
> This section also currently defines 'bakersdozen' as 13, which I assume is
> included just for fun.

I forget why `bakersdozen' is in there.  The fact that `dozen' wasn't,
however, leads me to suspect that I actually found it in a reference.

> However it may be worthwhile including some other
> common words for numbers such as:
> pair                    P 2
> ten                     P 10
> dozen                   S 12
> score                   S 20
> hundred                 P 100
> thousand                P 1.0e3
> million                 P 1.0e6

I don't see a problem adding these.

> billion                 P 1.0e9
> trillion                P 1.0e12

Don't the British use `billion' to mean 1.0e12 (i.e. isn't the British
`billion' the USA's `trillion')?
 
> UNITS OF LENGTH section currently defines 'printers_point' & 'printers_pica'.
> I suggest changing definition of latter from
> printers_pica           P 4.217518e-3 meter
> to
> printers_pica           P 12 printers_point     # exact

Ok.
 
> I suggest allowing following aliases
> point                   P printers_point
> pica                    P printers_pica
> pc                      P printers_pica
> The abbreviation 'pt' is often used for printers_point, but this is already
> defined as pint!

Yes, one has to be carefull with abreviations. `pt' is commonly used for
pint.  I won't add `pc' because it can be confused with `pico c' (i.e.
0.0002997925 meter second-1).
 
> Another important printing unit of length is the 'big point', as used in
> PostScript.  This has the abbreviation 'bp'. So I suggest:
> big_point               P inch/72               # exact

Ok.

> bp                      S big_point

I'm wary of adding too many 2-character abbreviations but will if
pressed.  What do you think?
 
> UNITS OF TIME section currently defines 'fortnight', but not 'week' or 
> 'month'!
> I suggest following:
> week                    P 7 day
> lunar_month             P 29.530859 day

Ok.

> month                   P year/12               # mean calendar month

I'll add this -- even though a month isn't a twelfth of a year.  I
suppose it might be convenient.

> sidereal_month          P 27.321661 day
> tropical_month          P 27.321582 day

I don't have a reference handy and the above aren't 1/12 of the
corresponding years.  Are you certain about the coefficients?

--------
Steve Emmerson   <steve@xxxxxxxxxxxxxxxx>