Provided is a process for tag imaging and decoding of machine readable coded data which comprises a plurality of layouts. Each layout has at least order n rotational symmetry, where n is at least two. The layout encodes a first codeword comprising a sequence of at least n first symbols, the first symbols being distributed at n locations about a center of rotational symmetry of the layout such that decoding the first symbols at each of the n orientations of the layout produces n representations of the first codeword. Each representation includes a different cyclic shift of the first codeword and being indicative of the degree of rotation of the layout. Each representation also includes a second codeword comprising a number of second symbols, the second codeword being indicative of information regarding the respective layout. The process includes the steps of acquiring an image which includes said coded data, and identifying at least one layout. The process also includes decoding the layout to determine at least a representation of the first codeword, and determining a degree of rotation of the layout from the decoded representation.