DEVICE, SYSTEM, METHOD AND PROGRAM FOR SPECIFYING SHIP SPEED RELATIVE TO WATER

摘要

The purpose of the present invention is to provide a means for specifying an appropriate ship speed relative to water. A system 1 for specifying a ship speed relative to water is installed in a ship and outputs the ship speed relative to water of the ship to, for example, a display device used by a user. If the ratio between the ship speed relative to water measured by a ship-speed-relative-to-water meter 11 and the propeller rotation speed measured by a tachometer 13 changes significantly, a data processing device 14 determines that the ship speed relative to water measured by the ship-speed-relative-to-water meter 11 is abnormal. In this case, the data processing device 14 calculates the propeller slip during the period in which the ship speed relative to water was last measured normally and calculates the ship speed relative to water in the period in which the abnormality in the measured ship speed relative to water was detected on the basis of the propeller rotation speed during the period in which the abnormality in the measured ship speed relative to water was detected and the calculated propeller slip.