Pat, I'm not sure there is any "gaping hole." The radian is the only possible coherent unit for angle, and is in Table 3, as already noted. The degree (and minute and second of arc) are accepted for use in Table 6 along with other "everyday" units like liter, metric ton, hectare, and time units of minute, hour, day. Further there is an ISO-31 recommendation that the degree be divided decimally, not into minutes and seconds (despite long standing practice in surveying, navigation, and astronomy. Those professions choose to make angles a PITA.) Your quad would be no more coherent in equations involving angle than the degree. I vote for the long-standing unit, as I see no material benefit to a new, incoherent unit. (I mean incoherent in the technical sense) NOTE: Sections 2.2.2 (final paragraphs) and 2.2.3 of NIST SP330 and SI Brochure have some remarks about the radian and other "dimensionless" units. I would say the radian has been pretty carefully considered, and there is zero chance of it going away.
--- On Wed, 3/25/09, Pat Naughtin <[email protected]> wrote: From: Pat Naughtin <[email protected]> Subject: [USMA:44109] Re: radians To: "U.S. Metric Association" <[email protected]> Date: Wednesday, March 25, 2009, 2:37 AM Dear Jim, Thanks for the reference. That solves one of my problems; the radian is listed as a part of the SI, but it does not begin to solve the second issue. It seems to me that there is a great gaping hole in the SI as long as it does not have a simple easy to use method for angle measurement for everyday practical applications. I cannot see that a builder of a table (say) will look at his work and remark, 'That leg looks like it's at the right angle — it's exactly π/2 radians,' or 'the corner of this hexagonal room looks OK at 2π/3 radians'. While the everyday users of angles (builders, sailors, air pilots, astronomers, surveyors, etc.) perceive that the SI does not have a unit for measuring angles quickly and easily, then the SI will be (probably mostly unconsciously) perceived as fundamentally flawed. I won't dwell on this issue. I agree with Pierre Abbat that I don't think that radians are going to go away any time soon. But I do think it's worthwhile occasionally to raise the thought of this rather largish hole in the structure of the SI. My suggestion about quads (symbol q) and milliquads (symbol mq) is just one suggestion to add to the many available solutions. Cheers, Pat Naughtin Geelong, Australia
