Patent ID: 8576506

Claim:
A disk drive comprising: a disk comprising a plurality of servo sectors defining a plurality of servo tracks, wherein: the servo tracks form a plurality of servo zones; and a servo data rate of servo sectors in a first servo zone is different than a servo data rate of servo sectors in a second servo zone; a head actuated radially over the disk, wherein the head comprises a read element separated from a write element by a reader/writer gap; and control circuitry operable to: synchronize a disk locked clock relative to the servo data rate of the servo zone the head is over; measure a first reader/writer gap in cycles of the disk locked clock at a first servo track in the first servo zone; measure a second reader/writer gap in cycles of the disk locked clock at a second servo track in the second servo zone; normalize the first and second reader/writer gaps to generate a normalized first and second reader/writer gaps; and estimate a third reader/writer gap in cycles of the disk locked clock at a third servo track in the second servo zone based on the normalized first and second reader/writer gaps.