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

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

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 More info about DAVE-ML: Simulation standards discussion listserv mailto:simstds@larc.nasa.gov