Patent ID: 8413027

Claim:
A method of decoding a coding pattern disposed on or in a substrate, said method comprising the steps of: (a) operatively positioning an optical reader relative to a surface of said substrate; (b) capturing an image of a portion of said coding pattern, said coding pattern comprising a plurality of square tags of length l identifying two-dimensional location coordinates, each tag comprising: a plurality n 1 of x-coordinate data symbols encoding a respective (n 2 , k) Reed-Solomon code for an x-coordinate; a plurality n 1 of y-coordinate data symbols encoding a respective (n 2 , k) Reed-Solomon code for a y-coordinate; a number z of said x-coordinate data symbols positioned in a central column of width q in each tag with a remaining (n 1 −z) x-coordinate data symbols distributed evenly on either side of said central column; and a number z of said y-coordinate data symbols positioned in a central row of said tag of width q with a remaining (n 1 −z) y-coordinate data symbols distributed evenly above and below said central row, wherein n 1 ≧n 2 and z≦1; (c) sampling and decoding at least one of: x-coordinate data symbols within said imaged portion; and y-coordinate data symbols within said imaged portion, wherein said imaged portion has a diameter of at least (l+q)√2 and less than (2l)√2 and is guaranteed to contain at least (n 1 +z)/2 data symbols from each of said Reed-Solomon codes, and wherein one or more symbol errors are correctable in each of said codes during said decoding.