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TIDE MEASUREMENT IN NAV MODE
A
P-3
TIDE MEASUREMENT IN NAV MODE
The accuracy of tide measurement in the NAV mode depends heavily on gyrocompass
accuracy.
Setting ship’s heading
The current indicator has a NAV mode which measures tides in deep waters where ground
tracking is not available. To achieve reliable measurements, however, you must feed
accurate heading (gyro) data and ship’s position (or speed and course) data to the current
indicator.
Procedure
1. Confirm that the gyro has settled and all necessary compensations (latitude
compensation, weather compensation, etc.) have been made correctly.
2. Adjust the AD Converter to show the same reading shown on the master gyrocompass.
(Do not make the adjustment while the ship is turning.)
If the gyro reading is accurate, the current indicator will provide accurate tide information. If
gyro data is wrong, the following symptoms will appear.
•
The drift angle in the ground tracking mode is not the same as that in the nav mode or is
shown in the direction reverse of the actual direction.
Drift angle in ground tracking mode: Difference between ground speed and course and
gyro heading
Drift angle in nav mode: Difference between nav course and gyro heading.
•
Tide speed and direction in the ground mode is not the same as that in the nav mode.
And the tide correlation (relative angle, size) between layers is different.
GT Mode NAV Mode
Appearance of tide vectors in ground tracking and nav modes when there is gyro error
If you encounter such symptoms calibrate the current indicator as shown in the installation
manual.