Abstract: Navigational apparatus adapted for interfacing between a Loran C receiver and an auto pilot is disclosed. The apparatus includes a reader for reading course error which is displayed on the readout panel of the receiver, a controller for inputting control signals to a vessel's auto pilot, which control signals direct the auto pilot to sheet straight ahead, correct left or correct right, and a computer for activating the controller in accordance with the data sensed by the reader. An audible alarm is included to alert a vessel's captain of a malfunction or an extreme off-course error so that the captain can manually effectuate any necessary corrective actions.