Nautical mile why

Speculative science. This sceptred isle. Root of all evil. Ethical conundrums. This sporting life. Stage and screen. Birds and the bees. Aren't ordinary miles good enough? However if I move one nautical mile along a meridian of longitude, the 'north south' lines on a map, my longitude changes by one minute of arc, which is one sixtieth of a degree. If I move along a great circle, the shortest distance between two points on the earth, one nautical mile again is one sixtieth of a degree.

Given that a different unit of distance us used at sea, the speed measurement also changes. It simply becomes nautical miles per hour, or knots. In the past, sailors would lower a wooden log over the stern of their ships to measure speed. The log was tied to a rope with knots tied along it. They would count the number of knots passing through their hands in a given time to get their speed. They measure the official speed of vessels. A measured mile is just a timed run between two points that are exactly 1 nautical mile apart.

Measured miles are still marked in many places around the UK. They are visible, with a transit marking the beginning and the end. The aviation and the space industry both also use nautical miles as their measure of distance.

When you look a the similarities between those, and the maritime industry it is clear why. All three navigate on a global scale. Planes and space craft also use knots for measuring their speed.

Just like with the maritime version, knots just measure nautical miles per hour. Using latitude and longitude coordinates is more practical for long-distance travel, where the curvature of the Earth becomes a factor in accurate measurement. Air and space travel also use latitude and longitude for navigation and nautical miles to measure distance.

The international nautical mile is used throughout the world. The measurement was officially set at exactly 1. Knots , on the other hand, are used to measure speed. One knot equals one nautical mile per hour, or roughly 1.