Abstract: The invention relates to a method and an apparatus for calibrating a positioning system, including control means (209) sending command signals to the positioning apparatus (204) intended during a working state to locate an object (203) in relation to an operating area (206), the situation of the apparatus being sensed and converted to an actual value signal which is sent to the control means. The positioning apparatus has a working state which is interrupted at given intervals by a calibrating state, during which the positioning apparatus is accurately put in register with at least one detector (208), situated within the operating area in a given position. The output signals from the detectors are allowed to activate the control means, whereafter the actual value signal is determined and the positioning apparatus calibrated in response to the determined actual value signal.