What is a microinch?
A microinch (µin) is the inch with the SI prefix micro, meaning one millionth, so 1,000,000µin make one inch.
The microinch is mostly seen in surface finish. US drawings give a part's roughness (Ra) in microinches, and a typical machined finish is 63µin, or 1.6µm.
A microinch is a millionth of an inch, which is exactly 0.0254 micrometers or 25.4 nanometers. Outside the US surface finish is given in micrometers instead.
What is an international nautical mile?
An international nautical mile is exactly 1,852 meters, which is about 1.15078 statute miles. The word 'nautical' distinguishes it from the statute mile used on land.
Because the nautical mile began as one minute of latitude, the Earth's circumference works out at roughly 21,600 nautical miles (360 degrees of 60 minutes each). Navigators measure distance directly off the latitude scale on a chart.
A tenth of a nautical mile is a cable, which is 185.2 meters and is still used for short distances at sea. Minutes and seconds belong to the angles of latitude and longitude, not to the unit itself.