knot (speed)

Information about knot (speed)

“Knots” redirects here. For other uses, see Knot (disambiguation).


A knot is a unit of speed. The abbreviation preferred by maritime authorities in the USA[1], and Canada [2], as well as the Institute of Electrical and Electronics Engineers and the International Bureau of Weights and Measures is kn.[3] [4] The abbreviation kt is also in widespread use, sometimes with kts for the plural (knots). It is a non-SI unit accepted for use with the SI.<ref name="nonSi" /> It is used around the world in meteorology and for maritime and aviation purposes.

Definition

1 international knot = 1 nautical mile per hour = 1.852 kilometres per hour exactly.

This is based on the internationally agreed length of the nautical mile. The international definition was adopted by the US in 1954 (which previously used the US nautical mile of 1853.248 m).[5] The international definition was adopted by the UK in 1970 which previously used the UK or Admiralty nautical mile of 1853.184 m. This is the definition used in most, if not all, modern circumstances. A common error that should be avoided is to use the term 'knot' to refer to the nautical mile itself.

The speed of a vessel relative to the fluid in which it travels is usually measured in knots. This may be referred to as 'boat speed', 'vessel speed' and, for aircraft, 'air speed'. For consistency in navigation, the speeds of relevant fluids, such as tidal streams, river currents and wind speeds, are also usually specified in knots. Knots are then also used to describe the actual speed of a vessel over the ground (SOG) and for its rate of progress toward a distant point ('velocity made good' or VMG).

Conversions

1 (international) knot is exactly equal to 1.852 kilometres per hour (km·h−1), and is approximately equal to the following:

Origin

Until the mid-19th century vessel speed at sea was measured using a chip log. This device consisted of a wooden panel, weighted on one edge to float upright, attached by line to a reel. The chip log was "cast" over the stern of the moving vessel and the line allowed to pay out. Knots placed at a distance of 47 feet 3 inches (14.4018 m) passed through a sailor's fingers, while another sailor used a 30 second sandglass (28 second sandglass is the current accepted timing) to time the operation. The knot count would be reported and used in the sailing master's dead reckoning and navigation. This method gives a value for the knot of 20.25 in/s, or 1.85166 km·h−1. The difference from the modern definition is less than 0.02%.

The chip log is also sometimes called the Knotted Rope.

Discussion

Although knots do not fit within the primary SI system, their retention for nautical and aviation use is important for navigational reasons, since the length of a nautical mile is almost identical to a minute of latitude. As a result, distance in nautical miles on a navigational chart can easily be measured by using dividers and the latitude indicators on the side of the chart.

Aeronautical terms

The following abbreviations are used to distinguish between various measurements of airspeed.

External links

See also

References

1. ^ Positions, Distances, Directions, Compass; Office of Coastal Survey, NOAA, USA
2. ^ POSITIONS, DISTANCES, DIRECTIONS, COMPASS, Ministry of Fisheries and Oceans, Canada
3. ^ See BIPM website on accepted non-SI units, in particular note f.
4. ^ IEEE guidelines for authors
5. ^ Louis E. Barbrow and Lewis V. Judson (1976). Appendix 4 The international nautical mile (PDF). Weights and Measures Standards of the United States, A brief history. NIST Physics Laboratory. Retrieved on 2007-08-02.
Knot may refer to:
  • knot – a fastening or securing of linear material such as rope, by tying or interweaving
  • List of knots
  • Knotted rope or quipu

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Institute of Electrical and Electronics Engineers

Type Professional Organization
Founded January 1, 1963
Origins Merger of the American Institute of Electrical Engineers and the Institute of Radio Engineers
Key people Leah H.
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International System of Units (abbreviated SI from the French Le Système international d'unités) is the modern form of the metric system.
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Si, si, or SI may refer to (all SI unless otherwise stated):

In language:
  • One of two Italian words:
  • sì (accented) for "yes"
  • si

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Meteorology (from Greek: μετέωρον, meteoron, "high in the sky"; and λόγος, logos, "knowledge") is the interdisciplinary scientific study of the atmosphere that focuses on weather processes and
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Shipping is physical process of transporting goods and cargo. Virtually every product ever made, bought, or sold has been affected by shipping. Despite the many variables in shipped products and locations, there are only three basic types of shipments: land, air, and sea.
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Aviation refers to all activities involving the operation of heavier-than-air aircraft, machines designed for atmospheric flight. The term also describes the organizations and regulatory bodies as well as the personnel related with the operation of aircraft and the industries
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1 nautical mile =
SI units
0 m 0 km
US customary / Imperial units
0 ft 0 mi
A nautical mile or sea mile is a unit of length.
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The hour (symbol: h, or occasionally hr; via Latin from Greek ὥρα "season, time span", ultimately cognate to English ) is a unit of time. It is not an SI unit but is accepted for use with the SI.
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Kilometres per hour (American English: kilometers per hour) is a unit of both speed (scalar) and velocity (vector). The unit symbol is km/h or km·h−1
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Airspeed is the speed of an aircraft relative to the air. There are several different measures of airspeed: indicated airspeed, calibrated airspeed, equivalent airspeed and true airspeed.
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    Tidal energy, sometimes called tidal power, is a form of hydropower that exploits the movement of water caused by tidal currents or the rise and fall in sea levels due to the tides.
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    river is a natural waterway that transits water through a landscape from higher to lower elevations. It is an integral component of the water cycle. The water within a river is generally collected from precipitation through surface runoff, groundwater recharge (as seen at baseflow
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    Wind speed is a term applied when talking about the movement of air from one place to the next.

    Please note, "Wind speed" should not be confused with the Speed of Wind. Analogous to the Speed of Sound or the Speed of Light, the Speed of Wind, at 3.
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    Ground speed is the speed of an aircraft relative to the ground. It is the sum of the aircraft's true airspeed and the current wind and weather conditions; a headwind subtracts from the ground speed, while a tailwind adds to it.
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    velocity is defined as the rate of change of position. It is a vector physical quantity, both speed and direction are required to define it. In the SI (metric) system, it is measured in meters per second (m/s). The scalar absolute value (magnitude) of velocity is speed.
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    Kilometres per hour (American English: kilometers per hour) is a unit of both speed (scalar) and velocity (vector). The unit symbol is km/h or km·h−1
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    1 foot =
    SI units
    0 m 0 mm
    US customary / Imperial units
    0 yd 0 in
    A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′
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    Feet per second (Or foot per second) is a unit of both speed (scalar) and velocity (vector quantity, e.g. 3ft/s west). It expresses the distance in feet (ft) traveled or displaced, divided by the time in seconds (s, or sec).
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    1 mile =
    SI units
    0 m 0 km
    US customary / Imperial units
    0 ft 0 yd
    “Miles” redirects here. For other uses, see Miles (disambiguation).

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    Miles per hour is a unit of speed, expressing the number of international miles covered per hour.

    Miles per hour is the unit used for speed limits, and speeds, on roads in the United Kingdom, United States and some other nations, where it is commonly abbreviated in everyday
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    Metre per second (U.S. spelling: meter per second) is an SI derived unit of both speed (scalar) and velocity (vector quantity which specifies both magnitude and a specific direction), defined by distance in metres divided by time in seconds.
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    A chip log, also called common log, ship log or just log, is a navigation tool used by mariners to estimate speed of a vessel through the water.

    Construction


    A chip log consists of a wooden board attached to a line (the log-line).
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    KNOT

    City of license Prescott, Arizona
    Broadcast area Flagstaff-Prescott, Arizona
    Branding 1450 KNOT Classic Country
    First air date 1957
    Frequency 1450 (KHz)
    Format Classic Country
    ERP 1,000 watts
    Class C
    Owner Guyann Corporation
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    1 foot =
    SI units
    0 m 0 mm
    US customary / Imperial units
    0 yd 0 in
    A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′
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    1 inch =
    SI units
    010−3 m 0 mm
    US customary / Imperial units
    010−3 ft 010−3 yd


    An inch (plural: inches; symbol or abbreviation: in or, sometimes,  
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    hourglass, also known as a sandglass or sand timer or sand clock, is a device for the measurement of time. It consists of two glass bulbs placed one above the other which are connected by a narrow tube.
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    Dead reckoning (DR) is the process of estimating one's current position based upon a previously determined position, or fix, and advancing that position based upon known speed, elapsed time, and course.
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    Navigation is the process of planning, recording, and controlling the movement of a craft or vehicle from one place to another.[1] The word navigate is derived from the Latin roots navis meaning "ship" and agere meaning "to move" or "to direct.
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    equator divides the planet into a Northern Hemisphere and a Southern Hemisphere, and has a latitude of 0. Latitude, usually denoted symbolically by the Greek letter phi, , gives the location of a place on Earth north or south of the equator.
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