"रेखांश": अवतरणों में अंतर

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==इतिहास==

 

[[चित्र:Longitude Vespucci.png|200px|left]]

==रेखांश का आकलन==

{{अनुवाद}}

 

Each degree of longitude is sub-divided into 60 [[minute of arc|minutes]], each of which divided into 60 [[arcsecond|seconds]]. A longitude is thus specified in [[sexagesimal]] notation as ''23° 27′ 30" E''. For higher precision, the seconds are specified with a [[Decimal#Decimal fractions|decimal fraction]]. An alternative representation uses degrees and minutes, where parts of a minute are expressed in decimal notation with a fraction, thus: ''23° 27.500′ E''. Degrees may also be expressed as a decimal fraction: ''23.45833° E''. For calculations, the angular measure usually must be converted to [[radians]], so longitude may also be expressed in this manner as a signed fraction of π ([[pi]]), or an unsigned fraction of 2π.

 

 

Longitude at a point may be determined by calculating the time difference between that at its location and [[Coordinated Universal Time]] (UTC). Since there are 24 hours in a day and 360 degrees in a circle, the sun moves across the sky at a rate of 15 degrees per hour (360°/24 hours = 15° per hour). So if the [[time zone]] a person is in is three hours ahead of UTC then that person is near 45° longitude (3 hours × 15° per hour = 45°). The word ''near'' was used because the point might not be at the center of the time zone; also the time zones are defined politically, so their centers and boundaries often do not lie on [[meridian (astronomy)|meridians]] at multiples of 15°. In order to perform this calculation, however, a person needs to have a [[marine chronometer|chronometer]] (watch) set to UTC and needs to determine local time by solar observation or astronomical observation. The details are more complex than described here: see the articles on [[Universal Time]] and on the [[Equation of time]] for more details.

!Latitude||N-S radius<br />of curvature,<br /> <math>M\;\!</math>||Degree of <br /> latitude|| ||E-W radius<br /> of curvature,<br /><math>N\;\!</math>||Degree of <br /> longitude

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