Abstract: A process for determining the center of data disk tracks. The transducer head is positioned to one side of a track. The head repeatedly reads the track and microsteps across the track. The number of microsteps taken at the position on each side of the center of the track where a certain number of error correction code errors occur, are designated as boundaries of that track. The center of the track is then calculated as being half-way between the boundaries. By using the microstep off-sets for the centers of two tracks on a data disk, a correction factor can be calculated to compensate for thermal expansion of the data disk.