MMC Navigation & Charting 3 — Questions and Answers
Question 1: What is the primary purpose of a danger bearing?
- To determine the vessel's speed over ground
- To establish a bearing that must not be crossed to avoid a hazard (Correct answer)
- To calculate the set and drift of a current
- To identify a safe anchorage using two bearings
Correct answer: To establish a bearing that must not be crossed to avoid a hazard
A danger bearing is a predetermined compass bearing to a fixed object; the navigator ensures the vessel stays on the safe side of this bearing to avoid a charted hazard.
Question 2: When using parallel rulers to transfer a course line to the compass rose, the transfer should always be made to the:
- Inner ring of the compass rose for true courses (Correct answer)
- Outer ring of the compass rose for magnetic courses
- Center dot of the compass rose
- Nearest meridian line for accuracy
Correct answer: Inner ring of the compass rose for true courses
The outer ring of a chart's compass rose shows true directions referenced to geographic north, while the inner ring shows magnetic directions.
Question 3: Which chart scale is considered the largest scale for harbor navigation?
- 1:80,000
- 1:20,000 (Correct answer)
- 1:500,000
- 1:1,000,000
Correct answer: 1:20,000
A scale of 1:20,000 (or smaller ratios like 1:10,000) is a large-scale chart showing fine detail suitable for harbor and port navigation.
Question 4: What action corrects for leeway when plotting a course to steer?
- Add the current set to the course
- Adjust the course into the wind by the estimated leeway angle (Correct answer)
- Subtract compass deviation from the magnetic course
- Apply variation from the compass rose to the true course
Correct answer: Adjust the course into the wind by the estimated leeway angle
Leeway is the sideways drift of a vessel caused by wind; the navigator compensates by steering upwind (into the wind) by the estimated leeway angle.
Question 5: A bearing of 000°T means the object is located:
- Due south of the observer
- Due east of the observer
- Due north of the observer (Correct answer)
- Due west of the observer
Correct answer: Due north of the observer
A true bearing of 000° (or 360°) indicates the object is directly due north of the observer, as true bearings are measured clockwise from true north.
Question 6: What is the charted symbol for a wreck that is considered dangerous to surface navigation?
- A solid dot with a circle
- A dagger symbol with depth in feet
- A crossed lines symbol with 'Wk' label (Correct answer)
- A sunken ship outline with a plus sign
Correct answer: A crossed lines symbol with 'Wk' label
A dangerous wreck on a nautical chart is depicted with crossed lines and labeled 'Wk', indicating a hazard that extends near enough to the surface to threaten vessels.
Question 7: When applying tide corrections for safe passage over a bar, the navigator should use:
- Mean high water (MHW) depth added to chart datum sounding
- Predicted tidal height for the date and time added to the charted depth (Correct answer)
- Mean lower low water (MLLW) subtracted from the charted sounding
- Half-tide level depth added to the observed depth
Correct answer: Predicted tidal height for the date and time added to the charted depth
To find actual depth at a bar, add the predicted tidal height for the specific date and time to the charted sounding (which is referenced to MLLW datum).
MMC Navigation & Charting 3
What is the primary purpose of a danger bearing?