Tides

Question 1

Spring tide

Answer 1

Caused by the sun and moon being approximately aligned. Higher high tides and lower low tides.

Question 2

Neap tides

Answer 2

Caused by the sun and mood being approximately at a right angle to each other.

Question 3

Mean tide

Answer 3

The mean average height of a tide is taken over a period of 19 years.

Question 4

MHWS

Answer 4

Mean high water springs: the mean high height of spring tides.

Question 5

MLWS

Answer 5

Mean low water springs: mean low water height of tidal spring.

Question 6

MHWN

Answer 6

Mean high water neap: mean high height of neap tide.

Question 7

MLWN

Answer 7

Mean low water neap: mean low height of neap tide.

Question 8

HAT

Answer 8

Highest astronomical tide that can be expected to occur under any combination of astronomical conditions.

Question 9

LAT

Answer 9

Lowest astronomical tide that can be expected to occur under any astronomical conditions.

Question 10

Range

Answer 10

The difference between HW AND LW

Question 11

Chart datum

Answer 11

Zero depth on the chart, charted depth and height of tides are measured from this datum.

Question 12

Drying height

Answer 12

An area that covers and uncovers under the movement of the tide.

Question 13

How is height of tide measured

Answer 13

Measured from chart datum to sea level.

Question 14

How is rise of tide measured

Answer 14

Measured from low water to sea level when tide is rising

Question 15

How is fall of tide measured?

Answer 15

Measured from previous high tide to sea level when tide is falling.

Question 16

How is charter height measured?

Answer 16

Measured above mean high water springs.