Allowance for tidal streams 1

In order to allow for the set and drift of the tide and to calculate the Course to steer – we begin as follows
We will assume that our Ground Track is 045 degrees true.
Draw in the ground track A – B and mark it with two arrow heads.
Note: we use 1 arrowhead for the indication of a water track, 2 arrowheads for a ground track and 3 arrowheads for the tidal stream or current.
Now we check the Standard Port to which the tidal streams refer.
On the chart we find out that it is “Portsmouth”.
With this information we enter the tide table.
We are interested in the morning High Water. The morning High Water on September 2nd is at 10:39 and the height is 4.3 meters.
To find out whether the rate of the tidal stream is a spring or a neap rate, we also have to take the height of the preceding Low Water into account, which is 0.1 meters.
To calculate the tidal range at this time we subtract the High Water from the Low Water.
Consequently the tidal range is 4.2 meters: 4.3 minus 0.1 meters.