Correction data signal diplexing onto the AM band

摘要

A method and apparatus for generating signals that can be used for accurately determining position and a method and apparatus for accurately determining position. A radio station modification unit is disclosed that can be incorporated into an existing radio transmission facility. The radio station modification unit generates a correction data signal that can be used by position determining systems for accurately determining position. In one embodiment, the radio station modification unit generates correction data that is encrypted. A position determination system decrypts the correction data upon receiving an activation instruction and uses the correction data to accurately determine position.