Abstract: A movable support (5) provided at its botton surface with a pad (19) made of antifriction material and slidable on a lapped reference surface (2).The movable support includes discharging jacks (8) which bear indirectly against the frame. The effort corresponding to the sum of the independent efforts of each jack must be lower than the effort exerted by the weight of the movable support and of its optional accessories, so as to minimize the difference between the sliding effort at the beginning and the friction effort of displacement in any direction on one plane and so as to limit, in the displacement referential X,Y,Z, the deviations of the geometrical positions of a sensor or of a tool. A motor (26) and a particular reducer drive the movable support in a translation direction X. There is provided a second drive unit for a translation in the direction Y.By using as an accessory a micrometric displacement table and a follower, it is possible to take tridimensional profilometric measurements.