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


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