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 and standardize the position of the points or other geometric elements on a manifold such as Euclidean space. The coordinates are ...
on a grid 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 systemalso called a projected coordinate reference system, planar coordinate system, or grid reference systemis a type of spatial reference system that represents locations on Earth using Cartesian coordinates (''x'', '' ...
, 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, heavily naval armour, armored warship with a main battery consisting of large naval gun, guns, designed to serve as a capital ship. From their advent in the late 1880s, battleships were among the largest and most form ...
; 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 game board 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 p ...
.http://www.fide.com/fide/handbook?id=125&view=article ''Appendices'' in World Chess Federation
The International Chess Federation or World Chess Federation, commonly referred to by its French acronym FIDE ( , ), is an international organization based in Switzerland that connects the various national chess federations and acts as the gove ...
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 Geographical feature, 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 ...
also use letters and numbers, typically several of each in order to specify many more locations over much larger regions.
References