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Re: 20000208: udunits - Galilean transforms

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  • Subject: Re: 20000208: udunits - Galilean transforms
  • Date: Wed, 09 Feb 2000 09:17:39 -0700
Brian,

> To: address@hidden
> From: address@hidden
> Subject: udunits - Galilean transforms
> Organization: .
> Keywords: 200002091546.IAA24383

In the above message, you wrote:

> I have recently been reviewing the Galilean transform features of the
> Udunits package and am confused by the following.  The manpage for the
> units library, udunits(3), contains the following statement:
> 
> > The Celsius scale is equivalent to the following unit:
> > 
> >           1.8 degF @ 32
> 
> But using the perl interface to udunits I find the following:
> 
> 1 (1.8 degF @ 32) == 15.2222222222223 (degC)
> 
> In other words, 1 unit of (1.8 degF @ 32) is equal to 15.2 degC.  This
> makes sense when you consider the offset to be relative to a unit of (1.8
> degF), i.e.,
> 
> 1 (1.8 degF @ 32) == 33 (1.8 degF) == 59.4 degF == 15.2 degC
> 
> So it looks to me that the unit (1.8 degF @ 32) is not equivalent to the
> Celcius scale.
> 
> Am I missing something?
> 
> Thanks,
> Brian
> 
> 
> Brian Eaton                               | email: address@hidden
> Climate Modeling Section                  |
> National Center for Atmospheric Research  |
> P.O. Box 3000, Boulder, CO  80307         |

You are correct.  The documentation is wrong.  The Celsius scale is
actually equivalent to the following unit specifications:

    1.8 degR @ 273.15

    1.8 degF @ 17.777777777777777

    degK @ 273.15

Regards,
Steve Emmerson   <http://www.unidata.ucar.edu>