The invention relates to a method for repositioning a numerically controlled device by using an image taken of an object as an aid. According to the method, the system is taught in such a way that a child image is defined for the camera's image, either its own set of co-ordinates is formed for the element or a set of coordinates is retrieved from elsewhere, and the image thus obtained, together with its co-ordinates, is stored in the data system, and, in the repositioning situation, the real-time image is compared with the child image stored in the data system, in order to determine the real-time position of the imaging device relative to the stored image. The set of co-ordinates used is a set of co-ordinates retrieved using satellite positioning, or the device's own internal set of co-ordinates. In the repositioning situation, the image stored in the teaching situation is sought as the co-ordinate point of the image stored in the memory is approached.