A system for generating position information includes a first set of image data, a second set of image data, and a processor. The first set of image data is generated to indicate the position of a surface plane marker. The second set of image data is generated to indicate the position of a retroreflector. The processor is configured to receive the first and second sets of image data and to generate position information indicative of the relative position of the surface plane marker relative to the retroreflector.