Abstract: A positioning system for positioning a movable body, such as an agricultural implement, with respect to a reference path constituted of at least one line of objects or a linear object, such as rows of crops. The system comprises a signal-echo distance-measuring device on the movable object and including a receiver for receiving an input signal representing the distance of the movable object in one direction from the reference path, and an input signal representing the distance of the movable object in the opposite direction from the reference path. The system compares both measured distances, and positions the movable object towards or away from the reference path to equalize the two measured distances.