Alphanumeric grid
Introduction    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  f6An '''alphanumeric grid''' (also known as '''atlas grid''') is a simple coordinate system 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, 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.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