Metric vs. other measurement systems - chart

[IntheGroove]

"Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth"...

[Toolmaker51]

"Earth's circumference has been used to define fundamental units of measurement of length: the nautical mile in the seventeenth century and the metre in the eighteenth"...

re nautical mile; Actual length is not regarded so often as it's rounded-off figure; to simplify mental calculations, ship handling poses many variables minute by minute.
https://en.wikipedia.org/wiki/Nautical_mile

"Historically, it was defined as one minute (1/60 of a degree) of latitude along any line of longitude. Today the international nautical mile is defined as exactly 1852 metres (6076 ft; 1.151 mi). The derived unit of speed is the knot, one nautical mile per hour."