1. A process for decoding machine readable coded data which comprises a plurality of layouts, each layout having at least order n rotational symmetry, where n is at least two, and encoding a codeword comprising a sequence of at least n symbols, the symbols being distributed at n locations about a center of rotational symmetry of the respective layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the codeword, each representation comprising a different cyclic shift of the codeword and being indicative of the degree of rotation of the layout, said process comprising: acquiring an image which includes said coded data with an image sensor; transmitting the acquired image to a computer system; identifying, at the computer system, at least one layout from the acquired image; decoding, at the computer system, the layout to determine at least a representation of the codeword; and determining, at the computer system, a degree of rotation of the layout from the decoded representation.