Navigation & Charting Flashcards

What does the term 'set' refer to in current navigation?

Answer: The direction toward which the current flows

Set is the direction toward which a current flows, expressed as a true bearing; it is paired with drift (speed) to fully describe a current.

A vessel's DR position differs from an EP (Estimated Position) because the EP:

Answer: Accounts for the effects of current, wind, and leeway

An Estimated Position (EP) is more accurate than a Dead Reckoning (DR) position because it incorporates known or estimated effects of current, wind, and leeway.

On a nautical chart, the term 'fathom' represents a depth equal to:

Answer: 6 feet

One fathom equals 6 feet; older U.S. charts used fathoms for soundings, though modern NOAA charts have converted to feet or meters.

What is the purpose of a 'tide rip' notation on a nautical chart?

Answer: It warns of turbulent water caused by opposing currents or shoaling

A tide rip notation warns mariners of an area where conflicting tidal currents or current flow over shoals creates turbulent, choppy, or dangerous water conditions.

When converting a magnetic course to a true course, the navigator should:

Answer: Add easterly variation and subtract westerly variation

To convert magnetic to true, add easterly variation (East is least in reverse: True = Magnetic + East variation) and subtract westerly variation.

Which NOAA publication provides the predicted times and heights of high and low waters for U.S. ports?

Answer: Tide Tables

NOAA's Tide Tables (now available online and as the Tides and Currents app) provide predicted times and heights of high and low water for U.S. reference and subordinate stations.

A vessel steaming at 12 knots on a course of 090°T for 2.5 hours has a DR position how far from the departure point?

Answer: 30 nautical miles due east

Distance = Speed × Time = 12 knots × 2.5 hours = 30 nautical miles; on a heading of 090°T (due east), the DR position is 30 nm east of departure.