An apparatus is configured to position a workpiece. The apparatus includes a planar base, and a movable stage configured to support the workpiece. The stage is configured to be moved over the planar base. The apparatus also includes an actuator configured to move the stage, a contactless position measurer configured to measure a position of the stage, and a first pump configured to generate a conditioned gas flow in a volume between the measurer and the stage. The base includes a plurality of gas channels provided in the base that provide a path of the conditioned gas flow through the base.