Patent ID: 7911727

Claim:
Apparatus for writing data to a data storage medium on which data is stored in data groups comprising tracks extending across said medium and spaced from a reference edge of said medium, the apparatus comprising: a control system operable to access data for determining a track reference difference value representative of a difference in a distance between the tracks of an existing data group on said medium and said edge and a distance between said edge and the tracks of a data group that is to be written to the medium such that it is the next data group following said existing data group and cause i) said data for determining a track reference difference value or ii) a track reference difference value determined using said data for determining a track reference difference value to be included in at least one frame that is to be written between said existing data group and said next data group such that tracks of said at least one frame are spaced from said edge by substantially the same distance as said tracks of the existing data group.