PURPOSE: To enable the setting of a ship speed at the optimum value, by a method wherein the initial memory position is turned by an angle of change in the course to calculate the resulting coordinate position when own ship is changed in the course so that the change in the position calculated always coincides with a moving distance of the ship.
CONSTITUTION: A position measuring device 1 measures the present position of own ship with a navigator and a bow bearing detector 2 outputs the bearing of own ship. A position measuring data memory circuit 3 stores a position measuring data to be outputted from the device 1 each clock from a timing circuit 4 and the position measuring data stored is introduced to a ship speed computing circuit 5 to compute the ship speed. When the track between two points is curved, a bearing data outputted from the device 2 is introduced to a course difference detection circuit 8 through latch circuits 6 and 7 to detect a difference between the preceding and current bearing data and the results are introduced to the ship speed computing circuit 5. The circuit 5 computes the position as given when the starting position between the two points is turned by an angle of change in the course in the direction of changing the own ship to calculate a displacement of position between the two points putting the position of turning computed as new starting point between the two points. Thus, movement per unit time is computed with the displacement of position defined as moving distance of the own ship.
MURAKAMI EIJI
ISHIHARA SHINJI
