Applying tide corrections to charted depth

Bowditch Ch. 9 §901

Bowditch Ch. 9 §901 — Tides and Tidal Currents Tides are the periodic vertical rise and fall of the sea level due to the gravitational interaction of the moon, sun, and earth. The principal lunar tide has a period of approximately 12 hours 25 minutes.

Bowditch Ch. 9 §902

Bowditch Ch. 9 §902 — Tides and Tidal Currents Spring tides occur near new and full moon and have the greatest range. Neap tides occur near first and last quarter moon and have the smallest range.

Bowditch Ch. 9 §903

Bowditch Ch. 9 §903 — Tides and Tidal Currents Tidal currents are the horizontal flow of water associated with the rise and fall of the tide. Flood is incoming, ebb is outgoing, slack water is the brief period of zero flow at the turn.

Bowditch Ch. 9 §904

Bowditch Ch. 9 §904 — Tides and Tidal Currents Charted soundings on US charts are referenced to Mean Lower Low Water (MLLW), the datum from which the tide tables predict the height of tide. Actual depth of water equals the charted sounding plus the predicted height of tide, and underkeel clearance equals that actual depth minus the vessel's draft. Heights of features such as bridges and lights are referenced instead to Mean High Water, so vertical clearance shrinks as the tide rises.

Bowditch Ch. 9 §905

Bowditch Ch. 9 §905 — Tides and Tidal Currents The NOAA Tide Tables predict the times and heights of high and low water, and the Tidal Current Tables the times of slack water and of maximum flood and ebb, at reference stations. Predictions for a nearby subordinate station are obtained by applying the tabulated time and height differences to its reference station. Always check the correct time zone and daylight time before applying a prediction.