Abstract: The invention provides an identifier system for computing identity information from image data. At least part of the image data is representative of an identifier. The identifier comprises a location element and encoded data associated with the location element. The identifier system comprises computer interpretable reference data corresponding to the identifier. The reference data is suitable for use in feature matching to determine a location and an orientation of the location element in the image data—thereby to locate the encoded data in the image data for subsequent decoding into the identity information The invention also provides a computer implemented method of presenting an augmented reality view of a physical article using the identifier system.