Method for determining a reference curve for the rotational position (φ) of a rotary component, which is rotatable about an axis of rotation, by means of a device comprising an encoder disc, which is connected to the rotary component and is rotatable about the axis of rotation, the encoder disc being designed as circular and having a periodic outer contour with N periods and a zero point, a beam source, which emits a measuring beam which is directed onto the outer contour of the encoder disc, a sensor unit comprising a first measuring area and a second measuring area, which is different from the first measuring area, and a control unit, which is connected to the sensor unit, wherein the periods of the outer contour are made up of a first function portion (51, 55) and a second function portion (52, 56), the first function portion (51, 55) and second function portion (52, 56) following a monotonic progression, one of the first and second function portions increasing monotonically and the other of the first and second function portions decreasing monotonically, the method comprising the following steps: ■ the measuring beam, which is directed onto the outer contour of the rotating encoder disc and onto the sensor unit, is recorded by the first measuring area as first measured values (M1.i) and by the second measuring area as second measured values (M2.j), ■ the first measured values (M1.i) and second measured values (M2.j) are transmitted from the sensor unit to the control unit, ■ the first measured values (M1.i) and associated first time values (T1.i) are shown by the control unit as a first measurement curve and the second measured values (M2.j) and associated second time values (T2.j) are shown as a second measurement curve, ■ the first measurement curve and second measurement curve are shifted relative to one another by the control unit until there is a phase difference of 90° between a phase-shifted first measurement curve and a phase-shifted second measurement curve, ■ the phase-shifted first measurement curve and phase-shifted second measurement curve are used by the control unit to determine first function values (R 1) for a number of first time values (T 1) and second function values (R 2) for a number of second time values (T 2) and the arctangent function according to the formula φ = tan − 1 R 1 R 2 is applied to the quotients of the first and second function values (R 1, R 2) and ■ the calculated function values are shown by the control unit as a progression over time and are stored as a reference curve for the rotational position (φ) of the rotary component. ■ the measuring beam, which is directed onto the outer contour of the rotating encoder disc and onto the sensor unit, is recorded by the first measuring area as first measured values (M1.i) and by the second measuring area as second measured values (M2.j), ■ the first measured values (M1.i) and second measured values (M2.j) are transmitted from the sensor unit to the control unit, ■ the first measured values (M1.i) and associated first time values (T1.i) are shown by the control unit as a first measurement curve and the second measured values (M2.j) and associated second time values (T2.j) are shown as a second measurement curve, ■ the first measurement curve and second measurement curve are shifted relative to one another by the control unit until there is a phase difference of 90° between a phase-shifted first measurement curve and a phase-shifted second measurement curve, ■ the phase-shifted first measurement curve and phase-shifted second measurement curve are used by the control unit to determine first function values (R 1) for a number of first time values (T 1) and second function values (R 2) for a number of second time values (T 2) and the arctangent function according to the formula φ = tan − 1 R 1 R 2 is applied to the quotients of the first and second function values (R 1, R 2) and ■ the calculated function values are shown by the control unit as a progression over time and are stored as a reference curve for the rotational position (φ) of the rotary component.