Abstract: A dimensional measuring and checking machine mounts a bridge structure (12) on legs (22) which are supported on a base (10) by air bearings. The varying forces due to travel of a probe mounting carriage (24) create vertical displacements of the bearings and movement of the bridge (12) out of alignment. To compensate for this, and thus enable high accuracy measuring, a chain (34) moves with the bridge (12), rotating a spindle (42) at one end of the machine, and thus moving the legs (22) at that end so levers (48) and pivot blocks (52) vary the height of the bridge (12).