![Europe Map](https://upload.wikimedia.org/wikipedia/commons/7/7d/Europe_Map_.svg)
A graticule (), on a
map
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
Many maps are static, fixed to paper or some other durable medium, while others are dynamic or interactive. Although ...
, is a graphical depiction of a
coordinate system as a
grid
Grid, The Grid, or GRID may refer to:
Common usage
* Cattle grid or stock grid, a type of obstacle is used to prevent livestock from crossing the road
* Grid reference, used to define a location on a map
Arts, entertainment, and media
* News ...
of lines, each line representing a constant
coordinate
In geometry, a coordinate system is a system that uses one or more numbers, or coordinates, to uniquely determine the position of the points or other geometric elements on a manifold such as Euclidean space. The order of the coordinates is sign ...
value.
It is thus a form of
isoline, and is commonly found on maps of many kinds at scales from the local to global.
The term is almost always used to specifically refer to the
parallels and
meridians of latitude and longitude respectively in the
geographic coordinate system. Grid lines for other
coordinate reference system
A spatial reference system (SRS) or coordinate reference system (CRS) is a framework used to precisely measure locations on the surface of the Earth as coordinates. It is thus the application of the abstract mathematics of coordinate systems and ...
s, such as
Universal Transverse Mercator
The Universal Transverse Mercator (UTM) is a map projection system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means i ...
, are commonly placed on maps for the same purposes, with similar meaning, and using similar design, but they are rarely called graticules. Some cartographers have used the term graticule to refer not only to the visual lines, but to the system of latitude and longitude reference itself;
[Dent, Borden D., Jeffrey S. Torguson, Thomas W. Hodler, ''Cartography: Thematic Map Design'', 6th Edition, McGraw-Hill, 2009, p.27] however, in the era of
Geographic information systems, this is far less common than calling it the
Geographic coordinate system.
History
![1482_Ulm_Ptolemy_World_Map](https://upload.wikimedia.org/wikipedia/commons/4/4e/1482_Ulm_Ptolemy_World_Map.jpg)
The graticule is of ancient origin, being almost as old as the concept of the
spherical earth,
coordinate system for measuring geographic locations, and the
map projection
In cartography, map projection is the term used to describe a broad set of transformations employed to represent the two-dimensional curved surface of a globe on a plane. In a map projection, coordinates, often expressed as latitude and longit ...
.
Strabo, in his ''
Geography'' (ca 20AD), states that the maps in
Eratosthenes's ''Geography'' Book 3 (3rd Century BC, now lost) contained lines "drawn from west to east, parallel to the equatorial line" (thus the term
parallel
Parallel is a geometric term of location which may refer to:
Computing
* Parallel algorithm
* Parallel computing
* Parallel metaheuristic
* Parallel (software), a UNIX utility for running programs in parallel
* Parallel Sysplex, a cluster of ...
)
Ptolemy
Claudius Ptolemy (; grc-gre, Πτολεμαῖος, ; la, Claudius Ptolemaeus; AD) was a mathematician, astronomer, astrologer, geographer, and music theorist, who wrote about a dozen scientific treatises, three of which were of importance ...
's ''
Geography'' (ca 150 AD) gives detailed instructions for drawing the
parallels and
meridians for his two
projections.
The works of Ptolemy and other classical geographers were available to the scientists of
medieval Islam. Some, such as
al-Khwarizmi, further developed these works, including creating maps on a graticule of latitude and longitude.
During the European
middle ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the post-classical period of global history. It began with the fall of the Western Roman Empire ...
, graticules disappeared from the few maps that were produced;
T and O map
A T and O map or O–T or T–O map (''orbis terrarum'', orb or circle of the lands; with the letter T inside an O), also known as an Isidoran map, is a type of early world map that represents the physical world as first described by the 7th-ce ...
s in particular were more concerned with religious
cosmology
Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher ...
than accurate representation of location. The
portolan chart
Portolan charts are nautical charts, first made in the 13th century in the Mediterranean basin and later expanded to include other regions. The word ''portolan'' comes from the Italian ''portulano'', meaning "related to ports or harbors", and wh ...
s of the 13th to 15th centuries were much more accurate, but used
rhumb lines that were much more useful for sea navigation than latitude and longitude. At the same time, however, the rediscovery of Ptolemy and other classical knowledge of the shape and size of the Earth led to the recreation of some of the ancient maps with their graticules; the earliest extant copies of Ptolemy's ''Geography'' with his maps date to the 14th and 15th centuries.
Starting in the 16th Century, the graticule has been ubiquitous on global and continental scale maps.
![Song Dynasty Map](https://upload.wikimedia.org/wikipedia/commons/4/48/Song_Dynasty_Map.JPG)
There is some debate over whether the Chinese and other Asians knew the world to be spherical prior to Western contact, but most maps appear to assume regions as flat.
Although Chinese maps do not portray any concept of latitude and longitude, cartesian grids appear on some maps dating back to the 11th Century.
Uses and Design
The graticule may serve several purposes on a map:
* Aid map users in estimating the coordinates of locations
* Aid map users in placing locations having known coordinates
* Indicate the cardinal directions, especially on map projections in which these directions vary across the map (e.g.
conic,
pseudocylindrical,
azimuthal)
[Slocum, Terry A., Robert B. McMaster, Fritz C. Kessler, Hugh H. Howard, ''Thematic Cartography and Visualization'', 3rd Edition, Pearson-Prentice Hall, 2009, p.201]
These are usually secondary to the primary purpose of the map, so graticules are often drawn to be relatively low in the
Visual hierarchy
Visual hierarchy, according to Gestalt psychology, is a pattern in the visual field wherein some elements tend to "stand out," or attract attention, more strongly than other elements, suggesting a hierarchy of importance. While it may occur natura ...
.
See also
*
Projected coordinate system
A projected coordinate system, also known as a projected coordinate reference system, a planar coordinate system, or grid reference system, is a type of spatial reference system that represents locations on the Earth using Cartesian coordinate ...
References
{{Reflist
Cartography