rekhaansh ko vikshanari,
ek mukt shabdakosh mein dekhein.
World map longlat.svg
pruthvi ka naksha
rekhaansh (λ)
rekhaansh ki rekhaaen is prakshep mein vakreeya prateet hoti hain, parantu dhruvavrutton ki aadhi hoti hain.
akshaansh (φ)
akshaansh ki rekhaaen is prakshep mein kshaitij evam seedhi prateet hoti hain, parantu ve bhinn ardhavyaason sahit vrutteeya hoti hain. ek akshaansh par di gain sabhi sthaan ekasaath judkar akshaansh ka vrutt banaate hain.
bhoomadhya rekha pruthvi ko uttari golaardh aur dakshini golaardh mein baantati hai, aur iska akshaansh shoonya ansh yaani 0° hota hai. World map with equator.svg
is sandook ko: dekhein samvaad

rekhaansh (IPA: /ˡaalɒaandʒaaɪaaˌaatjuːaad/), jise yoonaani akshar laimbada (λ) se darshit kiya jaata hai, poorv se pashchim paryant bhoogoleeya nirdeshaank hain, jinhein adhiktar maanachitrakala evam bhoomandaleeya nauvahan mein prayog kiya jaata hai. rekhaansh ki ek rekha ek dhruvavrutteeya rekha hoti hai, jo dhruvavrutt ka aadha hoti hai.



Longitude Vespucci.png

rekhaansh ka aakalan

Longitude is given as an angular measurement ranging from 0° at the prime meridian to +180° eastward and −180° westward. The Greek letter λ (lambda),[1][2] is used to denote the location of a place on Earth east or west of the prime meridian.

Each degree of longitude is sub-divided into 60 minutes, each of which divided into 60 seconds. A longitude is thus specified in sexagesimal notation as 23° 27′ 30" E. For higher precision, the seconds are specified with a 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.

For calculations, the West/East suffix is replaced by a negative sign in the western hemisphere. Confusingly, the convention of negative for East is also sometimes seen. The preferred convention—aathat East be positive—aais consistent with a right-handed Cartesian coordinate system with the North Pole up. A specific longitude may then be combined with a specific latitude (usually positive in the northern hemisphere) to give a precise position on the Earth's surface.

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 meridians at multiples of 15°. In order to perform this calculation, however, a person needs to have a 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
of curvature,
Degree of
E-W radius
of curvature,
Degree of
6335.44 km 110.574 km 6378.14 km 111.320 km
15° 6339.70 km 110.649 km 6379.57 km 107.551 km
30° 6351.38 km 110.852 km 6383.48 km 96.486 km
45° 6367.38 km 111.132 km 6388.84 km 78.847 km
60° 6383.45 km 111.412 km 6394.21 km 55.800 km
75° 6395.26 km 111.618 km 6398.15 km 28.902 km
90° 6399.59 km 111.694 km 6399.59 km 0.000 km


  1. Coordinate Conversion
  2. "λ = Longitude east of Greenwich (for longitude west of Greenwich, use a minus sign)."
    John P. Snyder, Map Projections, A Working Manual, USGS Professional Paper 1395, page ix


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