| 摘要 |
PURPOSE:To prevent a state in which a position cannot be detected by selectively using a loran C receiver and a self-supporting navigation device. CONSTITUTION:To a microcomputer 2, the self-supporting navigation device 8 consisting of the loran C receiver 4, an azimuth sensor 5, a travel distance sensor 6 and a navigation controller 7 is connected. The microcomputer 2 selects the loran C receiver 4 when the loran C receiver can detect the position, but selects the self-supporting navigation device 8 when it cannot defect the position. Only when a difference between a moving distance calculated from the detecting position of two times of the loran C receiver 4 and a moving distance detected by the self-supporting navigation device 8 is below a reference value, the self-supporting navigation device is switched to the loran C receiver 4. |
