wrote:
Jim Wilkins wrote:
US aviation uses a very strange hodgepodge mix of units..
Statute miles for visability

Even more strangely, the military opted to give some visibility in
meters.
http://www.bragg.army.mil/www-wx/taf_code.htm

Back in the 70's when I was young and a soldier,
the ranges were measured in meters and distance
was in "clicks". We still used inches and feet
for the smaller stuff.


Knots and nautical miles are based on degrees

Yes. As you say, that is the legacy and a useful approximation. The
earth is non-spherical (like a spinning top mated with a potato), and
a minute of arc can vary by up to 60 m in length. Various definitions
existed in the past but the nautical mile is now defined as 1852 m
precisely.
http://www.bipm.org/en/si/si_brochur...r4/table8.html