RE: Units of Measure for use in Math-ML datasets

[Jon Berndt]

Greetings [note that by default replies go to the poster - not the list]:

In JSBSim we are addressing this in our own way (at the moment), 
programmatically using an
STL map (indexed by STL strings) to index conversion factors like this:


  convert["M"]["FT"] = 3.2808399;
  convert["FT"]["M"] = 1.0/convert["M"]["FT"];
  convert["M2"]["FT2"] = convert["M"]["FT"]*convert["M"]["FT"];
  convert["FT2"]["M2"] = 1.0/convert["M2"]["FT2"];
  convert["FT"]["IN"] = 12.0;
  convert["IN"]["FT"] = 1.0/convert["FT"]["IN"];
  convert["LBS"]["KG"] = 0.45359237;
  convert["KG"]["LBS"] = 1.0/convert["LBS"]["KG"];
  convert["SLUG*FT2"]["KG*M2"] = 1.35594;
  convert["KG*M2"]["SLUG*FT2"] = 1.0/convert["SLUG*FT2"]["KG*M2"];
  convert["RAD"]["DEG"] = 360.0/(2.0*3.1415926);
  convert["DEG"]["RAD"] = 1.0/convert["RAD"]["DEG"];
  convert["LBS/FT"]["N/M"] = 14.5939;
  convert["LBS/FT/SEC"]["N/M/SEC"] = 14.5939;
  convert["N/M"]["LBS/FT"] = 1.0/convert["LBS/FT"]["N/M"];
  convert["N/M/SEC"]["LBS/FT/SEC"] = 1.0/convert["LBS/FT/SEC"]["N/M/SEC"];

  convert["M"]["M"] = 1.00;
  convert["FT"]["FT"] = 1.00;
  convert["IN"]["IN"] = 1.00;
  convert["IN3"]["IN3"] = 1.00;
  convert["DEG"]["DEG"] = 1.00;
  convert["RAD"]["RAD"] = 1.00;
  convert["M2"]["M2"] = 1.00;
  convert["FT2"]["FT2"] = 1.00;
  convert["KG*M2"]["KG*M2"] = 1.00;
  convert["SLUG*FT2"]["SLUG*FT2"] = 1.00;
  convert["KG"]["KG"] = 1.00;
  convert["LBS"]["LBS"] = 1.00;
  convert["LBS/FT"]["LBS/FT"] = 1.00;
  convert["N/M"]["N/M"] = 1.00;
  convert["LBS/FT/SEC"]["LBS/FT/SEC"] = 1.00;
  convert["N/M/SEC"]["N/M/SEC"] = 1.00;
  convert["PSI"]["PSI"] = 1.00;
  convert["INHG"]["INHG"] = 1.00;
  convert["HP"]["HP"] = 1.00;

Since this is only done at initialization time, CPU usage is not so critical 
for us. I'd
be interested in hearing more about standard unit abbrev.s, though.

Jon Berndt

Re: Units of Measure for use in Math-ML datasets

[Bruce Jackson]

Title: Re: Units of Measure for use in Math-ML
datasets


At 12:14 PM +1100 12/17/04, Brian, Geoff wrote:
Hi
all,
 
I noticed
in the DAVE-ML reference that the issue of units-of-measure notation
is still to be finalised.
I have
been looking at this for our flight dynamic / simulation modelling
here in DSTO, and have found that a number of the
proposed
standards have conflicting information for units of measure, both
between standards and within individual
standards.
As a
result, I have prepared a list of units of measure for use with
aircraft modelling here in DSTO (see attached). A
difference
I have
adopted from general conventions is the use of negative powers to
represent divisor units irrespective of whether
the
unit of
measure is metric or imperial (eg. ft s-1 instead of ft/s). I have
found this is simpler when defining something like
ft s-2
instead of ft/s/s or ft/s2.
 
 
I thought that this might be useful as a starting
point for defining a units-of-measure notation for Dave-ML and welcome
any comments.
 
The
references I have used for compiling the list
were:
    "Standards for the Exchange of
Simulation Modeling Data", Preliminary Draft, 9 June 1997, AIAA
Modeling and Simulation Technical Committee.
    "SI Units Dimensional Analysis
&, Chapter 8 Figure -- Conversion Tables", McMahonlines,
MathTech Reference Series.
    http://www.unc.edu/~rowlett/units/index.html
 
hope you
are having an enjoyable lead up to the end of the
year.
Regards
 
Mr Geoff Brian
Aircraft Flight Dynamics and Performance
Engineer.
Air Vehicles Division,
Defence Science and
Technology Organisation.


Brian,

Thanks for the legwork. This may make an excellent starting point
for satisfying the need to standardize units of measure
abbreviations.

I'd like to hear from other interested users on this important
issue. Brian is suggesting writing "ft s-1" instead of
"ft/s" for velocity in English units...

-- Bruce

P.S. Merry Christmas to those that celebrate it (like me).

P.P.S. When does Australia celebrate it (*grin*)? Do you sing
"Sleigh Ride" or "Dreaming of a White Christmas"?
-- bjax
-- 

Bruce Jackson <[EMAIL PROTECTED]>
Guidance and Controls Branch
18C West Taylor Street MS 132  
Research & Technology Directorate
NASA Langley Research
Center  Hampton, Virginia
23681
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