Yachtmaster revision module 11 of 20
Tidal heights, tidal curves, tidal diamonds, stream atlases, and secondary port corrections.
11 guided lessons · 23 practice questions · 20 flashcards
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Tides are caused primarily by the gravitational pull of the Moon (and to a lesser extent the Sun) on the Earth's oceans. As the Earth rotates, bulges of water follow the Moon, creating th...
When the Sun and Moon align (new moon and full moon), their gravitational pulls combine, producing spring tides — the highest highs and lowest lows. When the Sun and Moon are at right ang...
Chart Datum (CD) is the reference level from which depths on charts and tidal heights are measured. It is set at approximately the Lowest Astronomical Tide (LAT) — the lowest tide that ca...
Tide tables list the predicted times and heights of high water (HW) and low water (LW) for standard ports, for every day of the year. They are published in the nautical almanac (or the de...
Use the tidal-curve method printed for the named standard port and the edition in use. Begin with the correct HW and LW times and heights, calculate the range, establish whether the tide...
Most ports are listed as secondary ports, with differences applied to a nearby standard port. The almanac provides time differences (e.g., HW is 20 minutes later) and height differences o...
Tidal diamonds are lettered positions on the chart (e.g., diamond A, B, C) that give the set (direction) and rate (speed) of the tidal stream for each hour relative to HW at a reference p...
Tidal-stream set and rate affect track, speed over ground and passage time. Build the stream from the chart, diamond or atlas information valid for the relevant hour and range, then compa...
This is a fictional, non-navigational worked example; use the corrections and curve instructions in the current publication for a real port. The standard port HW is 0535 at 5.2 m and LW i...
Tides & Tidal Streams at Yachtmaster level is not just recall. The answer has to show command judgement, evidence quality, margin, and a fallback if the first plan stops being safe.
Decision pressure: The berth or bar may still be reachable, but not necessarily with a defensible under-keel clearance.
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