Dictionary Definition
graticule n : a network of fine lines, dots,
cross hairs, or wires in the focal plane of the eyepiece of an
optical instrument [syn: reticle, reticule]
User Contributed Dictionary
English
Noun
 A grid of horizontal and vertical lines.
 In the context of "specificallygeography": The network of lines of latitude and longitude that make a up a coordinate system such as the one used on the Earth.
 A square or rectangular region created by a graticule.
Extensive Definition
 For the use of coordinates on Wikipedia pages see: Wikipedia:WikiProject Geographical coordinates
A geographic coordinate system enables every
location on the earth to be specified, using mainly a
spherical coordinate system. There are three coordinates:
latitude, longitude and geodesic height.
The earth is not a sphere, but an irregular changing
shape approximating to an ellipsoid; the challenge is to
define a coordinate system that can accurately state each
topographical feature as an unambiguous set of numbers.
Latitude and longitude
 For discussion of latitude on Wikipedia pages see: Latitude
Latitude
(abbreviation: Lat. or (φ) pronounced phi ) is the angle from a
point on the earth's surface and the equatorial plane, measured from
the centre of the sphere. Lines joining points of the same latitude
are called parallels,
and they trace concentric circles on the surface of the earth,
parallel to the equator. The north pole 90°
N; the south pole 90°
S. The 0° parallel of latitude is designated the equator. The
equator is the
fundamental plane of all geographic coordinate systems. The
equator divides the globe into the Northern and Southern
Hemispheres.
Longitude
(abbreviation: Long. or (λ)pronounced lambda) is the angle east or
west of north–south line between the two geographical poles, that
passes through an arbitrary point. Lines joining points of the same
longitude are called meridians.
All meridians are halves of great circles, and are not parallel.
They converge at the north and south poles.
The line passing through the (former)
Royal Observatory, Greenwich (near London in the UK) has
been chosen as the international zerolongitude reference line, the
Prime
Meridian. Places to east are in the eastern hemisphere, and
places to the west in the western hemisphere. The antipodal
meridian of Greenwich is both 180°W and 180°E. The choice of
Greenwich is arbitrary, and in other cultures and times in history
other locations have been used as the prime meridian.
By combining these two angles, the horizontal
position of any location on Earth can be specified.
For example, Baltimore,
Maryland (in the USA) has a
latitude of 39.3° North, and a longitude of 76.6° West (). So, a
vector drawn from the center of the earth to a point 39.3° north of
the equator and 76.6° west of Greenwich will pass through
Baltimore.
Graticule perspective
This latitude/longitude "webbing" is known as the conjugate graticule. In defining an ellipse, the vertical diameter is known as the conjugate diameter, and the horizontal diameter——which is perpendicular, or "transverse", to the conjugate——is the transverse diameter. With a sphere or ellipsoid, the conjugate diameter is known as the polar axis and the transverse as the equatorial axis. The graticule perspective is based on this designation: As the longitudinal rings——geographically defined, all great circles——converge at the poles, it is the poles that the conjugate graticule is defined. If the polar vertex is "pulled down" 90°, so that the vertex is on the equator, or transverse diameter, then it becomes the transverse graticule, upon which all spherical trigonometry is ultimately based (if the longitudinal vertex is between the poles and equator, then it is considered an oblique graticule).Degrees: a measurement of angle
 For a further discussion of angular measure on Wikipedia pages see: Angle
Geographic coordinates were first used by the
astronomer and geographer Ptolemy in his
Geographia
using alphabetic Greek
numerals based on sexagesimal (base 60)
Babylonian
numerals. This was continued by Muslim geographers using
alphabetic Abjad
numerals and later via Arabic
numerals. In these systems a full circle is divided into 360
degrees
and each degree is divided into 60 minutes.
Although seconds,
thirds, fourths, etc. were used by Hellenistic
and Arabic
astronomers, they were not used by geographers who recognized that
their geographic coordinates were imprecise. Today seconds subdivided decimally
are used. A minute is designated by ′ or "m" and the second is
designated by ″ or "s". Seconds can be expressed as a decimal
fraction of a minute, and minutes can be expressed as a decimal
fraction of a degree. The letters N,S, E,W can be used to indicate
the hemisphere, or we can use "+" and "" to show this. North and
East are "+", and South and West are "". Latitude and Longitude
can be separated by a space or a comma. Thus there are several
formats for writing degrees, all of them appearing in the same
Lat,Long order.
 DMS Degree:Minute:Second (49°30'02"N, 123°30'30") or (49d30m02.5s,123d30m30.17s)
 DM Degree:Minute (49°30.0'123°30.0'), (49d30.0m,123°30.0')
 DD Decimal Degree (49.5000°,123.5000°), generally with 4 decimal numbers.
DMS is the most common format, and is standard on
all charts and maps, as well as global positioning systems and
geographic information systems.
Geodesic height
To completely specify a location of a topographical feature on, in, or above the earth, one has to also specify the vertical distance from the centre of the sphere, or from the surface of the sphere. Because of the ambiguity of "surface" and "vertical", it is more commonly expressed relative to a more precisely defined vertical datum such as mean sea level at a named point. Each country has defined its own datum. In the United Kingdom the reference point is Newlyn. The distance to the earth's centre can be used both for very deep positions and for positions in space.The earth is not static, points move relative to
each other due to continental plate motion, subsidence and diurnal
movement caused by the moon and the tides. The daily movement can
be as much as a metre. Continental movement can be up to 10 cm a
year, or 10m in a century. A weather
system 'high' pressure area can cause a sinking of 5mm.
Scandinavia
is rising by 1 cm a year as a result of the recession of the last
ice age,
but neighbouring Scotland is only
rising by 0.2 cm. These changes are insignificant if a local datum
is used. Wikipedia uses the global GPS datum so these changes are
significant.
The width of one longitudinal degree on latitude
\scriptstyle\,\! can be calculated by this formula (to get the
width per minute and second, divide by 60 and 3600,
respectively):




 \frac\cos(\phi)M_r,\,\!




 \frac\cos(\phi)\sqrt,\,\!
Datums often encountered
Latitude and longitude values can be based on several different geodetic systems or datums, the most common being the WGS 84 used by all GPS equipment, and by Wikipedia. Other datums however are significant because they were chosen by national cartographical organisation as the best method for representing their region, and these are the datum used on printed maps. Using the latitude and longitude found on a map, will not give the same reference as on a GPS receiver. Coordinates from the mapping system can be sometimes be changed into another datum using a simple translation. For example to convert from ETRF89 (GPS) to the Irish Grid by 49m to the east, and subtracting 23.4m from the north. More generally one datum is changed into any other datum using a process called Helmert transformations. This involves, converting the spherical coordinates into Cartesian coordinates and applying a seven parameter transformation (a translation and 3D rotation), and converting back.In popular GIS software, data projected in
latitude/longitude is often specified via a 'Geographic Coordinate
System'. For example, data in latitude/longitude with the datum as
the North
American Datum of 1983 is denoted by
'GCS_North_American_1983'.
Geostationary coordinates
Geostationary satellites (e.g., television satellites ) are over the equator. So, their position related to Earth is expressed in longitude degrees. Their latitude does not change, and is always zero over the equator.See also
 Automotive navigation system
 Geographic information system (GIS)
 Geographic coordinate conversion
 Geocodes
 Geotagging
 Global Positioning System (GPS).
 Greatcircle distance the shortest distance between any two points on the surface of a sphere, and explains how to find that quantity if one knows the two latitudes and longitudes.
 Map projection
 Tropic of Cancer
 Tropic of Capricorn
 Universal Transverse Mercator coordinate system
 Utility pole#Coordinates on pole labels
References
 Portions of this article are from Jason Harris' "Astroinfo" which is distributed with KStars, a desktop planetarium for Linux/KDE. See http://edu.kde.org/kstars/index.phtml
External links
 pseudocylindrical projections usefully explains the most popular (eg, Robinson) 'orthophanic' projections
 Mathematics TopicsCoordinate Systems
 Geographic coordinates of countries (CIA World Factbook)
 Worldwide Geogr.Coordinates & Satellite images
 Global Gazetteer
 Verify Locality Tool
 Find your exact geo position
graticule in Tosk Albanian: Geografische
Lage
graticule in Amharic: የምድር መጋጠሚያ ውቅር
graticule in Arabic: إحداثيات جغرافية
graticule in Asturian: Sistema de Coordenaes
Xeográfiques
graticule in Bengali: ভৌগলিক স্থানাঙ্ক
ব্যবস্থা
graticule in Belarusian: Геаграфічныя
каардынаты
graticule in Belarusian (Tarashkevitsa):
Геаграфічныя каардынаты
graticule in Bavarian: Geografische
Koordinatn
graticule in Bulgarian: Географски
координати
graticule in Cebuano: Koordineyt
heyograpikal
graticule in Czech: Zeměpisné souřadnice
graticule in German: Geographische
Koordinaten
graticule in Dhivehi: Geographic coordinate
system
graticule in Estonian: Geograafilised
koordinaadid
graticule in Modern Greek (1453): Γεωγραφικές
συντεταγμένες
graticule in Spanish: Coordenadas
geográficas
graticule in Esperanto: Geografia koordinata
sistemo
graticule in Basque: Sare geografiko
graticule in Persian: دستگاه مختصات
جغرافیایی
graticule in French: Coordonnées
géographiques
graticule in Western Frisian: Geografyske
koördinaten
graticule in Scottish Gaelic: Cochomharran an
Domhain
graticule in Galician: Sistema de Coordenadas
Xeográficas
graticule in Gujarati: અક્ષાંશરેખાંશ
graticule in Korean: 지리 좌표계
graticule in Croatian: Zemljopisne
koordinate
graticule in Iloko: Heograpikal a
nagsasabtan
graticule in Indonesian: Sistem koordinat
geografi
graticule in Interlingua (International
Auxiliary Language Association): Systema geographic de
coordinatas
graticule in Icelandic: Hnit (landafræði)
graticule in Italian: Coordinate
geografiche
graticule in Javanese: Sistem koordinat
geografi
graticule in Georgian: გეოგრაფიული
კოორდინატები
graticule in Swahili (macrolanguage): Anwani ya
kijiografia
graticule in Lao: ພິກັດພູມສາດ
graticule in Latin: Coordinata geographica
graticule in Ligurian: Coordinæ
geografiche
graticule in Lombard: Cuurdinat geugrafich
graticule in Hungarian: Földrajzi
koordinátarendszer
graticule in Macedonian: Географски координатен
систем
graticule in Malayalam: ജ്യോഗ്രഫിക്
കോഓര്ഡിനേറ്റ് സിസ്റ്റം
graticule in Dutch: Geografische
coördinaten
graticule in Dutch Low Saxon: Geografische
koördinaoten
graticule in Japanese: 測地系
graticule in Neapolitan: Sëštém d'u cördënazjôn
gjögrafëxë
graticule in Norwegian: Jordens
koordinatsystem
graticule in Piemontese: Coordinà
geogràfiche
graticule in Low German: Geograafsche Laag
graticule in Polish: Współrzędne
geograficzne
graticule in Portuguese: Coordenadas
geográficas
graticule in Romanian: Coordonate
geografice
graticule in Quechua: Tinkurachina siwi
graticule in Russian: Географические
координаты
graticule in Albanian: Koordinatat
gjeografike
graticule in Simple English: Geographic
coordinate system
graticule in Slovak: Geografický súradnicový
systém
graticule in Slovenian: Geografski koordinatni
sistem
graticule in Serbian: Географске
координате
graticule in SerboCroatian: Geografski
koordinatni sistem
graticule in Sundanese: Sistim koordinat
géografi
graticule in Swedish: Jordens
koordinatsystem
graticule in Tamil: புவியியல் ஆள்கூற்று
முறை
graticule in Thai: พิกัดภูมิศาสตร์
graticule in Vietnamese: Hệ tọa độ địa lý
graticule in Turkish: Coğrafi koordinat
sistemi
graticule in Turkmen: Koordinatlar
graticule in Ukrainian: Географічні
координати
graticule in Venetian: Cordinade
giogràfeghe
graticule in Volapük: Koordinatasit
taledavik
graticule in Vlaams: Geografische
coördinoatn
graticule in Contenese: 地理座標系統
graticule in Chinese: 经纬度