| 摘要 |
PROBLEM TO BE SOLVED: To measure the position of a ship and to provide information while making a device to be brought into the ship inexpensive and small. SOLUTION: When base stations 12 installed at a shore measure the arrival angle of the communicating radio wave of a portable telephone set 11 brought into the ship 10, an operation control center 13 calculates the navigation position of the ship 10, a speed, a direction and a distance from the shore based on the arrival angle from the plurality of base stations 12 and monitors operation. Then, by comparing a present navigation position with the navigation plan of the ship 10 registered before leaving port in an operation plan information DB 22, when the present position is deviated from the plan or when the navigation position is within an operation sea area of bad weather according to obtained weather and sea condition information, warning is sent to the portable telephone set 11.
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