Tides

Question 1

Draw diagram and explain spring and neap tides

Answer 1

• Spring tides occur when the earth, moon and sun all line up. This is where tides are at their greatest range due to the most amount of gravitational pull. High highs, low lows.
• Neap tides occur when the sun and moon are at right angles to one another. This is where tides are at their smallest range. Low highs and high lows.

Question 2

Explain drying heights

Answer 2

• Drying heights are measured from chart datum, which is an imaginary line from which all soundings are referred to. If there was no tide, what is displayed on the chart for a drying height would be its true height.

Question 3

What is LAT and where is it used

Answer 3

• Lowest astronomical tide is the lowest tide that would be experienced under average met conditions.

Question 4

What is HAT

Answer 4

• Highest astronomical tide. This would be the highest tide to be experienced under average met conditions. Bridge heights are often measured from HAT.

Question 5

What is MHWS

Answer 5

• Mean high water springs is the average height of high water during spring tides.

Question 6

Set, Rate, Drift

Answer 6