For a train, plane, car, etc, I recommend we NOT belabor "coherent units" and just focus on using correct symbols, km/h. I can pretty well guarentee the public DOESN'T want to know the speed in meters per second and carry out a division by 3.6 (or 3600) to estimate "when do we get there."
You are certainly (technically) correct that kilometers per hour isn't coherent units. However, for the most common calculation done with the data, it is more useful in everyday life. That is probably why the BIPM explicitly allows the hour to be used with the SI. If AP doesn't accept the authority of the SI Brochure, NIST SP330 and SP811, etc, there is not much we can do to convince them. Since the AP Style Guide requires online subscription or purchase, I don't have it. But we need someone who has it to analyze it's metric usage against the defining SI documents and call the errors to AP's attention. It might also make sense to check whether the Government Printing Office is correct on the same points that AP is wrong on. That might strengthen the case. ________________________________ From: "[email protected]" <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Mon, March 29, 2010 8:43:20 PM Subject: [USMA:46998] Re: FW: Special Employee Advisory: Message from Joe Boardman Of course, speed in SI is in units of m/s or in its multiples by SI prefixes, e.g. km/s of a spacecraft. "km/h" is not coherent SI, and "kph" is *certainly not acceptable* in any version of units. Who has the clout to correct the AP? ---- Original message ---- >Date: Mon, 29 Mar 2010 19:28:54 -0400 >From: "Carleton MacDonald" <[email protected]> >Subject: [USMA:46997] FW: Special Employee Advisory: Message from Joe >Boardman >To: "U.S. Metric Association" <[email protected]> > > Arrrgh. The Associated Press Stylebook strikes > again ... > > > > Carleton > > > > From: MacDonald, Carleton > Sent: Monday, March 29, 2010 12:59 > To: Employee Communications > Subject: RE: Special Employee Advisory: Message from > Joe Boardman > > > > The Associated Press Stylebook is rather clueless - > in fact, flat-out wrong - on a number of issues > regarding metric measure, and this is one of the > more egregious ones. > > > > For one thing, there is no unit of distance called a > "k". Capitalized, "K" is the SI (International > System of Units = the metric system) symbol for > "Kelvin", the base unit of thermodynamic > temperature. This is of course not what is meant > here. The unit of length being used here is the > kilometer, and its symbol - its only symbol - is > "km", and the way to show distance over time is > "km/h". "kph" in SI is meaningless, but no doubt > they're deriving it from "mph", under the wrong > assumption that as the "m" stands for "mile", the > "k" stands for "kilometer". > > > > The fact that AP and many other users have no idea > how to properly express metric units has other > examples too, such as "5K" road races (a 5-kelvin > race?). > > > > All of this of course stems from the fact that the > USA stubbornly resists joining the rest of the world > in measuring intelligently. > > > > That said: at least we mentioned the speed in SI as > well as in old units, and that is good. > > > > Carleton MacDonald > > ---------------------------------------------------- > > From: Employee Communications > Sent: Monday, March 29, 2010 10:41 > To: MacDonald, Carleton > Subject: RE: Special Employee Advisory: Message from > Joe Boardman > > > > Thanks for the input. But, according the Associated > Press Stylebook, kph is acceptable in all > references. > > > > Kevin > > > > ---------------------------------------------------- > > From: MacDonald, Carleton > Sent: Friday, March 19, 2010 3:38 PM > To: Employee Communications > Subject: RE: Special Employee Advisory: Message from > Joe Boardman > > > > One tiny minor thing: kilometers per hour is > expressed "km/h". > > > > ---------------------------------------------------- > > From: Employee Communications > Sent: Friday, March 19, 2010 15:32 > Subject: Special Employee Advisory: Message from Joe > B. > > > > Attached is a Special Employee Advisory from > President and CEO Joe B.. Please post on all > bulletin boards. > > > > special employee advisory > > March 19, 2010 > > > > > > Dear Co-workers, > > > > <snip> > > > > Specifically, this department will work on the > planning and development activities that will allow > us to significantly increase operating speeds above > 150 mph (240 kph) on the Northeast Corridor. It will > also pursue partnerships with states and others in > the passenger rail industry to develop > federally-designated high-speed rail corridors such > as the new projects moving forward in California and > Florida. > >
