Machine-readable coded data disposed on or in a substrate. The coded data includes a plurality of layouts of two or more layout types, each layout having n identical sub-layouts rotated 1/n revolutions apart about a center of rotation. Each layout encodes a first codeword formed from a sequence of n first symbols, each sub-layout defining a position for a respective first symbol so that the first symbol indicates the identity of the sub-layout. The layout also encodes a second codeword formed from a number of second symbols, which indicative of information regarding the respective layout and a number of third symbols which are partially indicative of a third codeword.
CROSS REFERENCE TO RELATED APPLICATION
The present application is a Continuation of U.S. application Ser. No. 10/409,864 filed on Apr. 9, 2003 the entire contents of which are herein incorporated by reference.
Machine-readable coded data disposed on or in a substrate. The coded data includes a plurality of layouts, each of which has order n rotational symmetry. The layout encodes a first codeword formed from a sequence of n first symbols distributed at n locations about the center of rotational symmetry of the layout. In use, decoding the first symbols at each of the n orientations of the layout produces n representations of the first codeword, with each representation being a different cyclic shift of the first codeword so as to indicate the degree of rotation of the layout. The layout also encodes a second codeword formed from a number of second symbols, the second codeword being indicative of information regarding the respective layout.
