An alphanumeric grid (also known as atlas grid) is a simple
coordinate system
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 sig ...
on 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 ...
in which each cell is identified by a combination of a letter and a number.
An advantage over numeric coordinates such as
easting and northing
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 coordina ...
, which use two numbers instead of a number and a letter to refer to a grid cell, is that there can be no confusion over which coordinate refers to which direction. As an easy example, one could think about
battleship
A battleship is a large armour, armored warship with a main artillery battery, battery consisting of large caliber guns. It dominated naval warfare in the late 19th and early 20th centuries.
The term ''battleship'' came into use in the late 1 ...
; simply match the number at the top to the number on the bottom, then follow the two lines until they meet in a spot.
Algebraic chess notation uses an alphanumeric grid to refer to the squares of a
chessboard
A chessboard is a used to play chess. It consists of 64 squares, 8 rows by 8 columns, on which the chess pieces are placed. It is square in shape and uses two colours of squares, one light and one dark, in a chequered pattern. During play, the bo ...
.
[http://www.fide.com/fide/handbook?id=125&view=article ''Appendices'' in World Chess Federation Handbook: see part ''C.7'' of section ''C. Algebraic notation''. Retrieved 2010-03-22.]
Some kinds of
geocode
A geocode is a code that represents a geographic entity ( location or object). It is a unique identifier of the entity, to distinguish it from others in a finite set of geographic entities. In general the ''geocode'' is a human-readable an ...
also use letters and numbers, typically several of each in order to specify many more locations over much larger regions.
References
Coordinate systems