the NATO unit of angle is the 'mil' and this is useful because
1 mil ~ 1 metre at 1 km
6400 mil = 2000pi mrad = 360 deg
** end memory
When I calculated 2000 x pi, I got 6238.185, and although this is approximately equal to 6400 mil, it is not sufficiently precise for it to be used as the basis of a measuring system. At best it is an approximation or a reasonably good 'rule of thumb'.
As I understand it. the mil is only used for artillery aiming so the slight deviation from the true milliradian is of no practical importance. Probably 20 rad is the largest that is used.
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
