MIRIAD has recently been upgraded to correctly handle image coordinates (the mapping between pixel and physical coordinates) in a correct fashion. Previously a linearised approximation was used, which was adequate for small fields, provided high astrometric accuracy was not required. The coordinates (and their description within the dataset) are treated in a fashion similar to AIPS (see Eric Greisen's AIPS memo (No. 27) `` Non-linear coordinate systems in AIPS '').