DWO Chart Work and Pilotage 3

Question 1

What is the primary official source of tidal predictions for US coastal waters?

Accepted Answer

NOAA Tide Tables

Answer

NOAA publishes official tidal predictions for US coastal waters in its Tide Tables, which are the authoritative reference for tidal information.

Question 2

What is 'slack water' in tidal terminology?

Accepted Answer

The brief period when tidal current velocity is zero between flood and ebb

Answer

Slack water occurs at the transition between flood and ebb currents when current velocity momentarily reaches zero before reversing direction.

Question 3

In IALA Region B (Americas), what color marks the port-hand side of a channel when entering from seaward?

Accepted Answer

Green

Answer

In IALA Region B (used in US waters), green buoys mark the port (left) side of a channel entering from seaward, consistent with the 'Red Right Returning' rule.

Question 4

What type of buoy is a nun buoy and what does it typically mark in US waters?

Accepted Answer

A conical red buoy marking the starboard side of a channel entering from seaward

Answer

Nun buoys are conical-shaped and painted red, marking the starboard side of a channel when entering from seaward in IALA Region B (US) waters.

Question 5

What is the 'rule of twelfths' used for in tidal calculations?

Accepted Answer

Estimating tidal height at any hour during the tidal cycle

Answer

The rule of twelfths approximates tidal height change as 1/12, 2/12, 3/12, 3/12, 2/12, 1/12 of the tidal range per successive hour, allowing quick depth estimation.

(DWO) Deck Watch Officer Practice Test

(DWO) Deck Watch Officer Practice Test

DWO Chart Work and Pilotage 3