Free OUPV Chart Plotting and Piloting Questions and Answers 1 — Questions and Answers
Question 1: You plot a course of 120° True from your last known position. The variation is 12° West and your compass has a deviation of 4° East. What is the correct compass course (PSC) to steer?
- 112°
- 128° (Correct answer)
- 136°
- 124°
Correct answer: 128°
To find the Compass course from a True course, you must correct for both variation and deviation. A common mnemonic is "True Virgins Make Dull Company, Add Whiskey" (True, Variation, Magnetic, Deviation, Compass, Add West). When going from True to Compass, you add Westerly variation and subtract Easterly variation. Then, you add Westerly deviation and subtract Easterly deviation. In this case: True (120°) + Variation (12°W) = Magnetic (132°). Magnetic (132°) - Deviation (4°E) = Compass (128°).
Question 2: While underway, you determine your Dead Reckoning (DR) position at 1400 is at LAT 34°10.5'N, LON 076°40.2'W. At the same time, you obtain a GPS fix that places you at LAT 34°11.5'N, LON 076°38.2'W. Which of the following correctly describes the set and drift you have experienced?
- Set is approximately 243° True, Drift is 2.2 knots.
- Set is approximately 063° True, Drift is 2.2 knots. (Correct answer)
- Set is approximately 063° True, Drift is 1.5 knots.
- Set is approximately 243° True, Drift is 1.5 knots.
Correct answer: Set is approximately 063° True, Drift is 2.2 knots.
Set is the direction the current is pushing you, and drift is the speed. The 'set' is the direction from the DR position to the actual Fix. The fix is to the Northeast of the DR position, so the direction (set) is roughly 063° True. The 'drift' is the distance between the DR and the fix, divided by the time. The distance is approximately 2.2 nautical miles. Assuming a one-hour run (implied by the question format), the drift is 2.2 knots.
Question 3: On a nautical chart for U.S. waters (IALA-B), you are returning from sea and see a green and red horizontally banded buoy with the top band being green. The shape is conical (a nun buoy). What does this buoy indicate?
- A safe water mark, proceed with caution.
- An isolated danger, pass well clear on any side.
- The preferred channel is to port, with the secondary channel to starboard.
- The preferred channel is to starboard, with the secondary channel to port. (Correct answer)
Correct answer: The preferred channel is to starboard, with the secondary channel to port.
In the IALA-B system used in the U.S., red and green horizontally banded buoys mark a junction where the channel splits (a preferred channel buoy). The top color indicates the primary or preferred channel. Since the top band is green and you are returning from sea ('Red Right Returning'), the preferred channel is to starboard (you would keep this buoy on your port side).
Question 4: What is the key difference between a Dead Reckoning (DR) position and an Estimated Position (EP)?
- A DR is based on celestial observation, while an EP is based on GPS.
- An EP is a DR position that has been corrected for the effects of current and leeway. (Correct answer)
- A DR position is always more accurate than an EP.
- An EP is only plotted at night, while a DR can be plotted at any time.
Correct answer: An EP is a DR position that has been corrected for the effects of current and leeway.
A Dead Reckoning (DR) position is calculated based only on your vessel's ordered course and speed through the water. An Estimated Position (EP) starts with the DR position but then applies corrections for known or estimated external factors like current (set and drift) and wind (leeway), making it a more accurate estimate of your actual location than a DR alone.
Question 5: You are plotting a course on a nautical chart with a scale of 1:80,000. On the latitude scale at the side of the chart, one minute of latitude is equal to:
- One statute mile.
- One kilometer.
- One nautical mile. (Correct answer)
- A distance that varies depending on the longitude.
Correct answer: One nautical mile.
Regardless of the chart's scale, one minute of latitude is universally accepted as being equal to one nautical mile. This is a fundamental principle of nautical chart measurement and is used for determining distance on most marine charts.
Question 6: Which of the following chart symbols represents a safe water mark?
- A black and red horizontally banded pillar.
- A yellow can or nun buoy.
- A red and white vertically striped sphere or buoy. (Correct answer)
- A green can with an odd number.
Correct answer: A red and white vertically striped sphere or buoy.
A safe water mark indicates that there is navigable water all around the mark. It is characterized by red and white vertical stripes. It can be a spherical buoy, a pillar, or a spar. If lighted, it shows a white light, often Morse Code 'A' (dot-dash).
Free OUPV Chart Plotting and Piloting Questions and Answers 1
You plot a course of 120° True from your last known position.
The variation is 12° West and your compass has a deviation of 4° East.
What is the correct compass course (PSC) to steer?