Alphanumeric grid

	a	b	c	d	e	f
1	a1	b1	c1	d1	e1	f1
2	a2	b2	c2	d2	e2	f2
3	a3	b3	c3	d3	e3	f3
4	a4	b4	c4	d4	e4	f4
5	a5	b5	c5	d5	e5	f5
6	a6	b6	c6	d6	e6	f6

Example of an Alphanumeric board

An alphanumeric grid (also known as atlas grid ^[1] ) is a simple coordinate system on a grid in which each cell is identified by a combination of a letter and a number. ^[2]

An advantage over numeric coordinates such as easting and northing, 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; 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. ^[3]

Some kinds of geocode also use letters and numbers, typically several of each in order to specify many more locations over much larger regions.

References

1. "Atlas grid". encyclopedia2.thefreedictionary.com. Retrieved 2010-03-22.
2. "Archived copy". Archived from the original on 2007-10-10. Retrieved 2010-03-22. Retrieved 2010-03-22.
3. 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.