A hydrostatic actuator comprises a gearing spindle with two elements which are rotatable relative to one another. A magnet element is mounted on the first element, and on the second element there are mounted a first magnetic field sensor for the determination of an absolute angular position of the two elements and a second magnetic field sensor for the provision of a signal indicative of a predetermined rotational position of the two elements. A method for determining a position of the actuator comprises steps for determining a first signal from the first magnetic field sensor and a second signal from the second magnetic field sensor, determining a rotational position of the first element with respect to the second element on the basis of the first signal, and checking the plausibility of the determined rotational position on the basis of the second signal. A control unit is provided for executing the method. A position sensor comprises the two magnetic field sensors for providing a first signal, which is indicative of the absolute position of the first element with respect to the second element, and a second signal, which is indicative of a predetermined rotational position of the two elements.