The books of voyages and adventures in films about desperate navigators, articles on the topic and geographic conversation between mariners often slips term "nautical mile".It's time to figure out what is the measure of length in shipping, seamen and why not use our usual kilometers.
What is 1 nautical mile?
Initially, this value corresponds to the length of 1/60 of a degree arc of a circle on the surface of the Earth with the center coinciding with the center of the planet.In other words, if we consider any meridian, the nautical mile will approximately equal to the length of one minute of latitude.Because the shape of the Earth is somewhat different from the shape of an ideal sphere, the length of 1 minute degree meridian consideration may differ slightly depending on the latitude.Most of the distance at the poles - 1861.6 m, and the least at the equator - 1842.9 m. To avoid confusion, it was proposed to unify the length of a nautical mile.For a basis the length of 1 minute at 45º degrees latitude (1852.2 m).This definition has led to what has become a nautical mile convenient to calculate navigational problems.For example, if you want to map to measure the distance of 20 miles, it is sufficient to measure the compass 20 arc minutes on any meridian, map.
Since 1954, the United States began to use international nautical mile (1852 meters).In practice, it is often rounded up to 1,800 meters.The official designation of this unit has not been accepted.Sometimes there is a reduction «nmi», «nm» or «NM».By the way, «nm» is the common designation of a nanometer.1/10 international nautical mile = 1 cable length = 185.2 meters.A 3-mile marine equal to 1 league.In the UK, it had often used its nautical mile is equal to 1853.184 meters. In 1929, Monaco hosted an international conference devoted to various issues of hydrography, which determined the length of a nautical mile to 1852.00 meters.Do not forget that the mile is not only marine but also land.In this case, its length 1,151 times smaller than the sea.
What is the relationship between nm and a node?
nautical mile (nautical mile) or as it is sometimes called, geographic or navigation, is widely used in geography, aviation and navigation.Since it is closely related to the concept of the marine unit used in the shipping industry as the basic unit rate.One unit is equal to one mile per hour traversed the vessel.The name "knot" due to the fact that in the old days ships used to measure the speed of lag.It was a log or a board in form of a triangle, which was attached to the goods.Such a sea anchor was tied lin (rope), which after a certain distance to tie knots.Lag dumped overboard, and then for a selected period of time (from 15 seconds to 1 minute) was calculated as units will go into the water.
There are different versions regarding the distance between nodes.Some believe that it was 25 feet (7.62 m), and if the 15 went to a single node, the result was obtained one nautical mile (100 ft / min).According to the second version, components tied through 47 feet 3 inches (14.4018 meters), and the count was 28 seconds.In this case, one unit showing the speed 101.25 ft / min.
hope now you will have no difficulty in understanding the marine terminology, and a mile from the nodes will be as clear as usual kilometers.
