Simple and Robust Binary Self-Location Patterns
  A simple method to generate a two-dimensional binary grid pattern, which allows for absolute and accurate self-location in a finite planar region, is proposed. The pattern encodes position information in a local way so that reading a small number of its black or white pixels at any place provides sufficient data from which the location can be decoded both efficiently and robustly. 
Alfred M. Bruckstein, Tuvi Etzion, Raja Giryes, Noam Gordon, Robert J.   Holt, and Doron Shuldiner
cs.IT math.IT