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Longman Dictionary of Contemporary English
line of latitude/longitude
▪ They were still travelling along the same line of longitude.
▪ He said he was trying to find the latitude and longitude of the nearest pie.
▪ In the course of their struggle to find longitude, scientists struck upon other discoveries that changed their view of the universe.
▪ By any name, the instrument soon helped sailors find their latitude and longitude.
▪ In spite of these obvious difficulties, Galileo had designed a special navigation helmet for finding longitude with the Jovian satellites.
▪ To prove worthy of the 20, 000 prize, a clock had to find longitude within half a degree.
▪ The town is at longitude 21° east.
▪ In the course of their struggle to find longitude, scientists struck upon other discoveries that changed their view of the universe.
▪ Perhaps there was a way to read longitude in the relative positions of the celestial bodies.
▪ The time signals must originate from places of known latitude and longitude.
The Collaborative International Dictionary

Heliocentric \He`li*o*cen"tric\ (h[=e]`l[i^]*[-o]*s[e^]n"tr[i^]k), Heliocentrical \He`li*o*cen"tric"al\ (h[=e]`l[i^]*[-o]*s[e^]n"tr[i^]*kal), a. (Astron.) pertaining to the sun's center, or appearing to be seen from it; having, or relating to, the sun as a center; -- opposed to geocentrical.

Heliocentric parallax. See under Parallax.

Heliocentric place, latitude, longitude, etc. (of a heavenly body), the direction, latitude, longitude, etc., of the body as viewed from the sun.


Refraction \Re*frac"tion\ (r?*fr?k"sh?n), n. [F. r['e]fraction.]

  1. The act of refracting, or the state of being refracted.

  2. The change in the direction of ray of light, heat, or the like, when it enters obliquely a medium of a different density from that through which it has previously moved.

    Refraction out of the rarer medium into the denser, is made towards the perpendicular.
    --Sir I. Newton.

  3. (Astron.)

    1. The change in the direction of a ray of light, and, consequently, in the apparent position of a heavenly body from which it emanates, arising from its passage through the earth's atmosphere; -- hence distinguished as atmospheric refraction, or astronomical refraction.

    2. The correction which is to be deducted from the apparent altitude of a heavenly body on account of atmospheric refraction, in order to obtain the true altitude.

      Angle of refraction (Opt.), the angle which a refracted ray makes with the perpendicular to the surface separating the two media traversed by the ray.

      Conical refraction (Opt.), the refraction of a ray of light into an infinite number of rays, forming a hollow cone. This occurs when a ray of light is passed through crystals of some substances, under certain circumstances. Conical refraction is of two kinds; external conical refraction, in which the ray issues from the crystal in the form of a cone, the vertex of which is at the point of emergence; and internal conical refraction, in which the ray is changed into the form of a cone on entering the crystal, from which it issues in the form of a hollow cylinder. This singular phenomenon was first discovered by Sir W. R. Hamilton by mathematical reasoning alone, unaided by experiment.

      Differential refraction (Astron.), the change of the apparent place of one object relative to a second object near it, due to refraction; also, the correction required to be made to the observed relative places of the two bodies.

      Double refraction (Opt.), the refraction of light in two directions, which produces two distinct images. The power of double refraction is possessed by all crystals except those of the isometric system. A uniaxial crystal is said to be optically positive (like quartz), or optically negative (like calcite), or to have positive, or negative, double refraction, according as the optic axis is the axis of least or greatest elasticity for light; a biaxial crystal is similarly designated when the same relation holds for the acute bisectrix.

      Index of refraction. See under Index.

      Refraction circle (Opt.), an instrument provided with a graduated circle for the measurement of refraction.

      Refraction of latitude, longitude, declination, right ascension, etc., the change in the apparent latitude, longitude, etc., of a heavenly body, due to the effect of atmospheric refraction.

      Terrestrial refraction, the change in the apparent altitude of a distant point on or near the earth's surface, as the top of a mountain, arising from the passage of light from it to the eye through atmospheric strata of varying density.

Douglas Harper's Etymology Dictionary

late 14c., "length," from Latin longitudo "length, duration," from longus (see long (adj.)). For origins, see latitude.


n. angular distance measured west or east of the prime meridian.


n. an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; "all points on the same meridian have the same longitude" [syn: meridian, line of longitude]

Longitude (TV series)

Longitude is a 2000 TV drama produced by Granada Productions and the A&E Network for Channel 4, first broadcast in 2000 in the UK on Channel 4 and the US on A&E. It is a dramatisation of the 1997 book of the same title by Dava Sobel. It was written and directed by Charles Sturridge and stars Michael Gambon as clockmaker John Harrison (1693–1776) and Jeremy Irons as horologist Rupert Gould (1890–1948).


Longitude ( or , British also ), is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees and denoted by the Greek letter lambda (λ). Meridians (lines running from the North Pole to the South Pole) connect points with the same longitude. By convention, one of these, the Prime Meridian, which passes through the Royal Observatory, Greenwich, England, was allocated the position of zero degrees longitude. The longitude of other places is measured as the angle east or west from the Prime Meridian, ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Specifically, it is the angle between a plane containing the Prime Meridian and a plane containing the North Pole, South Pole and the location in question. (This forms a right-handed coordinate system with the z axis (right hand thumb) pointing from the Earth's center toward the North Pole and the x axis (right hand index finger) extending from Earth's center through the equator at the Prime Meridian.)

A location's north–south position along a meridian is given by its latitude, which is approximately the angle between the local vertical and the plane of the Equator.

If the Earth were perfectly spherical and homogeneous, then the longitude at a point would be equal to the angle between a vertical north–south plane through that point and the plane of the Greenwich meridian. Everywhere on Earth the vertical north–south plane would contain the Earth's axis. But the Earth is not homogeneous, and has mountains—which have gravity and so can shift the vertical plane away from the Earth's axis. The vertical north–south plane still intersects the plane of the Greenwich meridian at some angle; that angle is the astronomical longitude, calculated from star observations. The longitude shown on maps and GPS devices is the angle between the Greenwich plane and a not-quite-vertical plane through the point; the not-quite-vertical plane is perpendicular to the surface of the spheroid chosen to approximate the Earth's sea-level surface, rather than perpendicular to the sea-level surface itself.

Longitude (book)

Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time is a best-selling book by Dava Sobel about John Harrison, an 18th-century clockmaker who created the first clock ( chronometer) sufficiently accurate to be used to determine longitude at sea—an important development in navigation. The book was made into a television series entitled Longitude. In 1998, The Illustrated Longitude was published, supplementing the earlier text with 180 images of characters, events, instruments, maps and publications.

Usage examples of "longitude".

Could it have been from one of these sources that he derived his accurate longitudes?

Oronteus Finaeus World Map also commands attention: it successfully places the coasts of Antarctica in correct latitudes and relative longitudes and finds a remarkably accurate area for the continent as a whole.

Total longitude between Gibraltar and the Sea of Azov is accurate to half a degree, while across the map as a whole average errors of longitude are less than a degree.

Layer upon layer, the cumulative effect of his painstaking and detailed analysis is to suggest that we are deluding ourselves when we suppose that accurate instruments for measuring longitude were not invented until the eighteenth century.

It is clear, too, that they had an instrument of navigation for accurately determining longitudes that was far superior to anything possessed by the peoples of ancient, medieval or modern times until the second half of the eighteenth century.

Then my eyes fell upon the vast planisphere spread upon the table, and I placed my finger on the very spot where the given latitude and longitude crossed.

We asked for and got a transpolar orbit on the twenty west, one-sixty east longitude.

A second is also in Bihar, at the same longitude as Asansol, but north of the Ganges River.

The earliest known maps of the mediaeval epoch present the appearance of rough delineations of land and water, a corrupted nomenclature, and no reference whatsoever to degrees of longitude or latitude.

But after Mercator it became possible for navigators to make use of latitude and longitude when plotting their courses.

In so doing the accuracy of his work declined: instruments capable of finding longitude did not exist in 1569, but appear to have been used to prepare the ancient source documents Mercator consulted to produce his 1538 map.

The proof of this is that if the Atlantic Island had 2300 leagues of longitude, and the distance of Cadiz to the mouth of the river Maranon or Orellana and Trinidad, on the coast of Brazil, is, not more than 1000, 900, or 1100 leagues, being the part where this land joined to America, it clearly appears that, to complete the complement of 2300 leagues, we have to include in the computation all the rest of the land from the mouth of the Maranon and Brazil to the South Sea, which is what they now call America.

Or why, irrespective of all latitudes and longitudes, does the name of the White Sea exert such a spectralness over the fancy, while that of the Yellow Sea lulls us with mortal thoughts of long lacquered mild afternoons on the waves, followed by the gaudiest and yet sleepiest of sunsets?

Moreover, these antagonist kingdoms, Tartarean and Elysian, defined as the everlasting habitations of departed souls, have been successively driven, as dissipated visions, from their assumed latitudes and longitudes, one after another, by progressive discovery, until now the intelligent mind knows of no assignable spot for them.

Although hardly one shell, crab or fish is common to the above-named three approximate faunas of Eastern and Western America and the eastern Pacific islands, yet many fish range from the Pacific into the Indian Ocean, and many shells are common to the eastern islands of the Pacific and the eastern shores of Africa, on almost exactly opposite meridians of longitude.