A method is given for finding a reference correction value of an index mark of an angular encoder. The angular encoder includes a first read head, a second read head, and a patterned element having incremental marks and an index mark. In a first instance and in a second instance, the patterned element is rotated relative to the read heads to obtain incremental readings from the first read head and the second read head and an index mark from the first read head. Based on these readings, a processor determines, in the first instance, a first reference position and, in the second instance, a second reference position. The processor determines the reference correction value based at least in part on the first reference position and the second reference position.