7.
Tide tables give the times and heights of high and low water for different ports. The times, which are presented in local zone time, may need to be adjusted if Daylight Saving Time (DST) is being kept during summer. Find the times and heights of high and low water at the following places; adjust for DST if required. Note whether the range is at: mean spring, mean neap or an intermediate point.
a) Victoria b) Victoria c) Victoria
d) Namley Harbour e) Namley Harbour f ) Namley Harbour g) Colville h) Colville i) Colville
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In the afternoon / evening of Thursday, 3rd January. In the afternoon / evening of Tuesday, 15th October. In the afternoon / evening of Monday, 25th November. Mid morning to mid afternoon on Wednesday, 24th April. On the morning of Thursday, 5th December On the morning of Sunday, 18th August.
In the afternoon / evening of Sunday, 28th April In the afternoon / evening of Saturday, 23rd November. On the morning of Sunday, 4th August.
A tidal curve can be used to find the height of tide between high and low water. Using the appropriate tidal curve find the height of the tide at the following places and note whether the tide is rising or falling.
a) Victoria on Thursday, 3rd January at 1600 UT b) Namley on Sunday, 18th August at 0600 DST c) Colville on Saturday, 23rd November at 1710 TZ - 0100
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Once the height of the tide has been found for a given place and time it can be applied to the chart’s datum. This enables navigators to make various essential calculations, for example: predicting what clearance there is likely to be under a moored vessel at low water. Calculating what clearance a vessel is likely to have when using a small craft channel or swashway. Working out the duration of a ‘safe clearance’ period at the shallow entrance of a harbour.
a) Place: Victoria Date: Saturday, 21st September
the mooring be at the next low water? b) Place: Port Fraser
Time: 1340 DST If a vessel is moored at Victoria in a depth of water of 6.0m at 1340 DST, what will the depth of water at Date: Wednesday, 11th September Time:13:30 DST What clearance will a vessel (draught 1.8m) have as it crosses the ‘least depth’ area of 0.7m in the inner
swashway near the entrance to Port Fraser? c) Place: Namley Harbour Date: Thursday, 24th October
on the rising tide.
At what time will the vessel need to return to have the same height of tide as it passes the tide gauge again, on the falling tide? d) Place: Colville
Date: Tuesday, 19th November Time: 0800 TZ - 0100
What depth of water will there be in Colville Marina (charted depth 3.1m) at 0800 TZ - 0100 on Tuesday, 19th November?
e) Place: Hamilton Sound Date Friday, 12th July Time: 1700 SPDST
What depth would be found along the 20m contour off Hamilton Sound at 1700 SPDST on Friday, 12th July?
Time: 1140 DST At 1140 DST a vessel leaving Namley Harbour passes the tide gauge at the entrance, which shows 2.6m,
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