| 摘要 |
PURPOSE:To detect a mileage, vehicle position average vehicle speed, etc. on a vehicle by using sign posts which are installed at equal intervals on a road side and emit signals of different frequencies depending upon the directions of roads. CONSTITUTION:Sign posts 1a-1n installed at equal intervals on the road side of a road transmit signals fn of different frequencies depending upon the directions of the road, that is, the azimuth where a vehicle travels. In a machine 2 loaded on the vehicle, the signals from the posts are received and the passage of the posts is known from the presence of absence of any carrier component by a carrier detecting part 6 and a sign post decision part 8. A frequency discriminating part 7 and a direction deciding part 9 determine directions from the frequencies of the posts. An arithmetic part 10 calculates mileage from the times of the passage through the posts, average speeds from the time when the vehicle passes the posts and said mileage and vehicle positions from the traveling direction and said mileage, respectively. |
