A method and a system for controlling the winding/unwinding of a rope portion onto/from a rotary drum, comprises the step of making available a rope which is at least partially wound onto a rotary drum, wherein the rope is guided from the rotary drum along a defined path as far as a hauling point, wherein a traction force acts on the rope beyond the hauling point. The method comprises unwinding or winding the rope by executing a rotation of the rotary drum, such that a defined rope portion is moved along the defined path; and determining the length of the defined rope portion in the region of the defined path. The method comprises determining an angle difference corresponding to the rotation of the rotary drum; and controlling the rotary drum for further winding/unwinding taking into account the length and the angle difference. A calibration in the region of the defined path during the use of the rotary drum provides a control for the rotary drum.