US Patent 7445160 Position location using error correction

Provided are codes that may be applied to a sheet of paper or other surface, as well as techniques for decoding such codes. Using such codes and decoding techniques permits identification of the position of a pen (e.g., a digital pen) on the paper or other surface, by observing only a small field of the surface. Moreover, the position often can be identified even in the presence of arbitrary rotation and certain errors (e.g., due to dust or stray markings on the paper).