Humans identify location and directions based on visual cues, such as landmarks, rather than a precise coordinate grid. A database of landmarks can be used to determine the location of a user who can merely describe their location in the same manner they would to any human contact. The location of the...http://www.google.de/patents/US20030176965?utm_source=gb-gplus-sharePatent US20030176965 - Landmark-based location of users
