1. A system for mapping a surface comprising: a projection device operative to project a sequence of parallel bars, each of said bars having one of a first and second light values, wherein a vector representation of the order of said bars, supplemented by a value representing an additional bar, is mutually orthogonal to any circular shift of said order supplemented by a value representing an additional bar; means for generating an image of the surface; and means for processing the resulting image to map the surface.