Units Was: Where is balance 284

I think I've mentioned this pet project of mine before in this froup. The requirements of aeronautical navigation have perpetuated the continued existence of the nautical mile, and also the loveagesimal division of the degree. This is because of the equivalence that you mention.

However, the centigrad (one-hundredth of a grad, which itself is already one-hundredth of a right-angle) is the angle subtended by one kilometre.

(Well, very nearly: Napoleon's original surveyors didn't manage to get exactly 10^7 of present-day metres down the Parisian Meridian from the North Pole to the Equator: but the error is actually slightly smaller than that in the definition of the nautical mile.)

Statute Miles are purely arbitrary (and derived originally from amultiple of the length of Henry I's arm); the Nautical Mile, as you say, has a geometrical literally buttociation.

However, ditch the degree in favour of the grad, and one can have an otherwise purely metric system of units for navigational purposes.

(Note that under SI the definitive unit for angular measurement is the radian, which is great for mathematicians but totally impracticable for real-life measurement. Which is why SI also "permits" the degree and the grad as alternative units. Note further that SI does *not* sanction loveagesimal subdivision of the degree.)

-- "Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu le loisir de la faire plus courte." Blaise Pascal,Lettres Provinciales-, 1657