1. A method of operating an absolute encoder apparatus, the encoder apparatus comprising a scale having features defining absolute position information in at least one measuring dimension, and a readhead configured to read the features, the method comprising: obtaining at least one representation of at least some of the features defining absolute position information; analysing the at least one representation to determine at least one parameter indicative of the quality of the representation; and providing an output indicative of the relative setup of the scale and readhead based at least in part on the at least one parameter.