Patent ID: 8358572

Claim:
A data storage device comprising: a first read mechanism; a second read mechanism; a data storage medium movable with respect to the first read mechanism and the second read mechanism; a first reference patch positioned substantially at a first corner of the data storage medium, the first reference patch containing reference bits disposed along both sides of at least one track, wherein the first read mechanism is configured to read the reference bits of the first reference patch as said first read mechanism travels along said at least one track; a second reference patch containing reference bits disposed along both sides of at least one track, the second read mechanism being configured to read the reference bits of the second reference patch as said second read mechanism travels along said at least one track of said second reference patch; and a controller configured to determine whether the first read mechanism and the data storage medium are offset with respect to each other based upon the reference bits read by the first read mechanism and the reference bits read by the second mechanism.