A stage assembly for positioning a device along a first axis, the stage assembly comprising: a base; a stage that retains the device and moves above the base; a mover assembly that moves the stage along the first axis relative to the base; a first sensor system that monitors the movement of the stage along the first axis, the first sensor system generating a first signal, the first sensor system having a first sensor accuracy; a second sensor system that monitors the movement of the stage along the first axis, the second sensor system having a second sensor accuracy that is different from the first sensor accuracy of the first sensor system, the second sensor generating a second signal; and a control system that controls the mover assembly using at least one of the first sensor and the second signal.