1. A method of teaching a robotic cleaning device a perimeter of an area of interest, comprising the steps of: positioning the robotic cleaning device so that an obstacle detecting device of the robotic cleaning device can monitor at least part of the area; controlling the obstacle detecting device of the robotic cleaning device to follow and continuously record a position of an object, while the object is moving along the perimeter of the area of interest; and creating positional data of the perimeter from the continuous recordings of the positions of the object.