An estimator is shown to accurately count tracks during a seek in a DVD or CDROM storage device. The estimator states are position and velocity. Although the gains can be adapted via the recursive Kalman equations, the track count accuracy suffers little degradation if the gains are fixed. The position estimate's bandwidth can be matched to the seek system poles affording optimum filtering. Although the input is a nonlinear function of position, the estimator is constructed in such a way as to maintain linearity.