A system comprises a rotatable object having a pseudo-random pattern of overlapping rounded shapes on an outer surface of the rotatable object and an image sensor configured to capture an image of a portion of the pseudo-random pattern on the outer surface. The system also comprises a memory configured to store a pattern map corresponding to the pseudo-random pattern on the outer surface of the rotatable object; and a processing unit configured to correlate the portion of the pseudo-random pattern in the captured image with a corresponding portion of the pattern map stored on the memory.