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Longitude by chronometer is a method, in navigation, of determining longitude using a marine chronometer, which was developed by John Harrison during the first half of the eighteenth century. It is an astronomical method of calculating the longitude at which a position line, drawn from a sight by sextant of any celestial body, crosses the ...
John Harrison (3 April [O.S. 24 March] 1693 – 24 March 1776) was an English carpenter and clockmaker who invented the marine chronometer, a long-sought-after device for solving the problem of how to calculate longitude while at sea.
A marine chronometer is a precision timepiece that is carried on a ship and employed in the determination of the ship's position by celestial navigation.It is used to determine longitude by comparing Greenwich Mean Time (GMT), and the time at the current location found from observations of celestial bodies.
The neutral density ( ) or empirical neutral density is a density variable used in oceanography, introduced in 1997 by David R. Jackett and Trevor McDougall. [1] It is a function of the three state variables (salinity, temperature, and pressure) and the geographical location (longitude and latitude).
Longitude calculations can be simplified using a clock is set to the local time of a starting point whose longitude is known, transporting it to a new location, and using it for astronomical observations. The longitude of the new location can be determined by comparing the difference of local mean time and the time of the transported clock.
There have been other subsequent studies. In 1994, Drinkwater et al. examined the latitude of the north wall from the 1970s to 1992 at each degree of longitude from 50 to 75°W, [3] and Miller analysed the onshore/offshore position of the north wall at 10 cross-isobath transects equally spaced between 75 and 80°W from 1976 to 1988. [4]
The sigma coordinate system is a common coordinate system used in computational models for oceanography, meteorology and other fields where fluid dynamics are relevant. [1] This coordinate system receives its name from the independent variable σ {\displaystyle \sigma } used to represent a scaled pressure level.
Cox designed a 2° latitude-longitude grid with up to 12 vertical levels at each point. With more and more research on ocean model, mesoscale phenomenon, e.g. most ocean currents have cross-stream dimensions equal to Rossby radius of deformation, started to get more awareness.