Abstract: An optical installation for determining the relative positions of at least two objects, such as vehicle wheels, includes two optical systems for determining the position of an object in space, each with respect to its observation frame. An optical reference system includes a target visible from the other optical system in the absence of the objects. The other optical system includes a device for analyzing an image of the target and a device for positioning the target with respect to its observation frame, so as to deduce therefrom the position of the observation frame of the other optical system with respect to the observation frame of the of the optical reference system, on the basis of the positions of the target with respect to the observation frame and of the target with respect to the observation frame of the optical reference system.