Patent US 4,253,149

A system for controlling the course of a vessel. A digital computer 22 receives information signals from a geographic position locator 20, such as a Loran-C receiver, a depth sounder, or a water temperature sensor, and is also capable of interactive communcations with a remote terminal 24 which is accessible by an operator of the vessel. The digital computer 22 continuously monitors the information signals and develops therefrom a digital output signal representing the sign and magnitude of vessel cross-track error. To obtain information required to determine cross-track error, and to obtain certain other information relating to the identity and type of the geographic position locator 20, the digital computer 22 transmits questions to the remote terminal 24 for display therby and evaluates responses made by the operator through remote terminal 24. The digital computer 22 may be enabled or disabled in response to instructions from the operator using remote terminal 24. The digital computer 22 may also be disabled during the existence of an alarm condition resulting from instability in the information signals, or upon detection of information in the information signals representing loss of tracking by the geographic position locator 20. An interface unit 30, which is enabled only when the digital computer 22 is enabled, converts the cross-track error information in the digital output signal into a corresponding analog cross-track error signal. After suitable amplitude scaling, the analog cross-track error signal is integrated, and the integrated signal is summed with the analog cross-track error signal, to develop a course correction signal which is adapted to be summed with a heading error signal in a conventional electronic automatic pilot, whereby the electronic automatic pilot is capable of maintaining the vessel at a desired heading and on a predetermined geographic track.