| 摘要 |
<p>A system which allows a central control unit to track automatically the positions of a fleet of mobile units. Each mobile unit carries a position updating apparatus which includes means (2) to determine its position, and processing means (4) in the form of computing equipment in communication with the position determining means. The processing means (4) in turn controls a transmitting means (6), such as a radio transmitter of the private mobile radio system that the mobile unit uses for communication, for transmitting information to the central control. The position determining means (2) and processing means (4) are arranged to send the latest position of the mobile unit to the central control at intervals. The processing means (4) stores a number of rules for determining the interval between the transmission of position update messages to the central control. These rules are based upon the direction of travel of the mobile unit and other factors, such as its location.</p> |
