Measuring the tidal stream.
If you need an accurate measure of the direction and rate of the tidal stream the published figures on charts or atlases are of minimal use.
One approach to obtaining the most accurate information is to turn in to the current when close to a buoy. If the vessel's speed is adjusted to that the buoy remains in transit with a point on the shore and the vessel does not move towards or away from the mark the instruments aboard can be used to measure the tide.
The compass heading will be the reciprocal of the direction and the log will show the speed of the current.
This can be very useful when navigating over relatively short distances in fog.
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