Nautical Miles to Chains
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1 nautical mile (nmi) = 92.0623558 chain (ch). Nautical Mile (nmi) is a unit of Length used in Standard system. Chain (ch) is a unit of Length used in Standard system.

Nautical Mile: A Unit of Length

A nautical mile is a unit of length that is used in air, marine, and space navigation, and for the definition of territorial waters. It is based on the Earth’s longitude and latitude coordinates, and is equal to one minute of arc along a meridian. In this article, we will explore the definition, history, uses, and conversions of the nautical mile.

Definition of the Nautical Mile

The nautical mile is defined as exactly 1,852 metres (6,076 feet; 1.151 miles) by the International Hydrographic Organization (IHO) since 1929. This definition is based on the length of one minute of arc along a great circle of a sphere having the same surface area as the Clarke 1866 ellipsoid, which approximates the shape of the Earth.

The nautical mile is not an SI unit, but it is accepted for use with the SI by the International Committee for Weights and Measures. The derived unit of speed is the knot, which is one nautical mile per hour.

History of the Nautical Mile

The concept of the nautical mile dates back to ancient times, when navigators used the stars and angles to measure distances at sea. The word mile comes from the Latin phrase mille passus, meaning a thousand paces.

The nautical mile was originally defined as the length on the Earth’s surface of one minute of arc along a meridian (north-south line of longitude). However, this definition varied depending on the latitude and the shape of the Earth assumed by different countries. For example, France defined a nautical mile as one ten-millionth of a quarter meridian using the original 1791 definition of the metre.The United States and the United Kingdom used an average arcminute based on the Clarke 1866 ellipsoid.

In order to standardize the nautical mile, the IHO adopted the current definition in 1929, which was later endorsed by other international organizations such as the International Civil Aviation Organization (ICAO) and the International Maritime Organization (IMO). The United States adopted the international nautical mile in 1954 and the United Kingdom in 1970.

Where Nautical Mile is Used

The nautical mile is widely used in navigation, especially for maritime and aviation purposes. It is convenient to use because it corresponds to one minute of latitude, which can be easily measured with a sextant or a GPS device. It also allows for simple calculations of distances along great circles, which are the shortest routes between two points on a sphere.

Some examples of where nautical mile is used are:

• The definition of territorial waters, which are usually 12 nautical miles from a country’s coastline.
• The measurement of flight levels and air routes for aircrafts.
• The determination of speed limits and fuel consumption for ships and boats.
• The designation of marine protected areas and fishing zones.
• The mapping of ocean currents and wind patterns.

How to Convert Nautical Mile

The nautical mile can be converted to other units of length using simple multiplication or division by a conversion factor. Here are some common conversion factors:

For example, to convert 10 nautical miles to kilometres, we multiply by 1.852:

10 NM × 1.852 = 18.52 km

To convert 50 kilometres to nautical miles, we divide by 1.852:

50 km ÷ 1.852 = 27 NM

Example Conversions of Nautical Mile to Other Units

Here are some example conversions of nautical mile to other units:

• 1 NM = 1,852 m
• 1 NM = 6,076 ft
• 1 NM = 1.151 mi
• 1 NM = 0.54 leagues
• 1 NM = 10 cables
• 1 NM = 800 fathoms
• 1 NM = 2,025 yd

Chain: A Unit of Length Used for Measuring Land

The chain is a unit of length that is equal to 66 feet or 22 yards or 4 rods or 100 links. It is part of the US customary and imperial measurement systems. It is used for measuring land, especially in surveying and mapping. The symbol for chain is ch. There are 10 chains in a furlong, and 80 chains in one statute mile. An acre is the area of 10 square chains. The unit is named after the chain, a measuring device that was invented by Edmund Gunter, a clergyman and mathematician, in the 17th century. The chain is also sometimes called a Gunter’s chain, a surveyor’s chain or a land chain. In this article, we will explore the definition, history, usage and conversion of the chain as a unit of length.

Definition of the Unit

The chain is a unit of length that is equal to 66 feet or 22 yards or 4 rods or 100 links. It is one of the base units in the US customary and imperial measurement systems, along with the foot, the yard and the mile. The chain is also a derived unit in the International System of Units (SI), which is the most widely used system of measurement in the world. The SI base unit of length is the meter, which is defined as the length of the path travelled by light in vacuum during a time interval of 1/299792458 seconds.

The definition of the chain has not changed since its introduction by Edmund Gunter in 1620, who based it on an earlier English unit called an acre’s breadth, which was equal to one-tenth of a furlong or one-eightieth of a mile. However, the definition of the foot, which is used to define the chain, has changed several times over time, as different standards and methods of measurement were adopted by various countries and regions. The current definition of the foot as 0.3048 meter was agreed upon by an international treaty in 1959.

History of the Unit

The origin of the chain as a unit of length can be traced back to 1620, when Edmund Gunter created a measuring device called a chain. The chain was 66 feet long and consisted of 100 metal links connected by three rings each. The links were made of thick wire with a loop at each end. The chain had brass handles at each end for holding and folding. Gunter chose this unit because it was convenient for his work on surveying and mapping land. He also named this unit after himself, as he wrote in his book: "I have taken as unit for these measurements one hundredth part [of a furlong], which I will call an Chain".

Gunter’s unit was soon adopted by other surveyors and mapmakers, who found it useful for measuring distances and areas on flat or gently sloping land. The chain was also used for laying out roads, railways and canals. The chain became part of the US customary and imperial measurement systems, which were based on earlier English units that were brought by British settlers to America. The chain was also used in some other countries influenced by British practice, such as Canada and India.

In 1785, when the United States Congress passed the Land Ordinance Act to survey and divide the public land west of the Appalachian Mountains into rectangular townships and sections, the use of the chain as a unit of measurement was mandated by law. The act also defined the chain as equal to four rods or poles or perches. The surveyors who carried out this work were known as "chain bearers" or "chain carriers", and they marked each mile along their survey lines with wooden posts called "milestones".

In 1959, when the United States, Canada, the United Kingdom and some other Commonwealth countries agreed to adopt a common definition of the foot as 0.3048 meter, based on the international yard that was defined as 0.9144 meter by an international treaty in 1959, the chain became exactly equal to 20.1168 meters.

Usage of the Unit

The chain is a unit of length that is used for measuring land, especially in surveying and mapping. The chain is also used for measuring distances on roads, railways and canals. The chain is still used in some rural areas and historical contexts in the United States, Canada and some other countries that follow the US customary or imperial measurement systems.

The chain is used for various purposes, such as:

• Measuring length, width and area of land parcels and properties.
• Measuring distances and dimensions on maps and plans.
• Measuring boundaries and borders between states, counties and townships.
• Measuring road widths and lengths.
• Measuring railway track gauges and lengths.
• Measuring canal widths and depths.

How to Convert

The chain can be converted to other units of length by using conversion factors or formulas. Here are some examples of how to convert chains to other units of length in the US customary system, the imperial system and the SI system:

• To convert chains to feet, multiply by 66. For example, 10 ch = 10 × 66 = 660 ft.
• To convert chains to yards, multiply by 22. For example, 10 ch = 10 × 22 = 220 yd.
• To convert chains to miles, divide by 80. For example, 10 ch = 10 / 80 = 0.125 mi.
• To convert chains to centimeters, multiply by 2011.68. For example, one ch = one × 2011.68 = 2011.68 cm.
• To convert chains to meters, multiply by 20.1168. For example, one ch = one × 20.1168 = 20.1168 m.
• To convert chains to kilometers, divide by 49.7097. For example, 10 ch = 10 / 49.7097 = 0.2012 km.

Equivalents in Other Units and Scales

The chain can be expressed in terms of other units of length by using equivalent values or ratios. Here are some examples of how to express chains in other units of length:

• One chain is equal to four rods or poles or perches.
• One chain is equal to one-tenth of a furlong or one-eightieth of a mile.
• One chain is equal to one-hundredth of a league or one-fortieth of a league (US).
• One chain is equal to one-hundred-millionth of an astronomical unit or one-forty-billionth of a light-year.
• One chain is equal to one-thousandth of a nautical mile or one-three-thousand-six-hundredth of a degree of latitude or longitude.