Patent ID: 7688540

Claim:
A disk drive comprising: a disk; a head actuated radially over the disk; and control circuitry operable to: position the head over a first radial location; select a first data tracks per inch (TPI_ 1 ) for data tracks recorded near the first radial location; position the head over a second radial location; select a second data tracks per inch (TPI_ 2 ) for data tracks recorded near the second radial location; position the head over a third radial location; select a third data tracks per inch (TPI_ 3 ) for data tracks recorded near the third radial location; and estimate a geometry of the head in response to TPI_ 1 , TPI_ 2 and TPI_ 3 , wherein: the first radial location is near a middle diameter of the disk; the second and third radial locations are near one of an inner diameter of the disk and an outer diameter of the disk; the head comprises a write width WW 0 estimated according to 1/(TPI_ 1 ·cos αs 1 ), where αs 1 is a head skew angle at the first radial location; the head further comprises a bevel angle α and a pole height H; the bevel angle α and the pole height H are estimated according to a two variable equation: TPI — 2=[WW 0 ·cos·(α s 2 )+ H ·sin(α s 2 −α)/cos(α)] −1 TPI — 3=[WW 0 ·cos·(α s 3 )+ H ·sin(α s 3 −α)/cos(α)] −1 where: αs 2 is a head skew angle at the second radial location; αs 3 is a head skew angle at the third radial location; and α and H are computed by solving the two variable equation in response to TPI_ 2 and TPI_ 3 .