MMC Navigation & Charting 2 — Questions and Answers
Question 1: On a nautical chart, what does a blue tint in shallow water areas indicate?
- Deep water safe for large vessels
- Water depth less than the chart datum sounding (Correct answer)
- Areas where anchoring is prohibited
- Submerged rocks and wrecks
Correct answer: Water depth less than the chart datum sounding
Blue tinting on nautical charts indicates shallow water areas where depths are less than the charted datum, warning mariners of potential hazards.
Question 2: What is the magnetic variation on a nautical chart?
- The difference between true north and compass north caused by local magnetic anomalies
- The difference between true north and magnetic north due to Earth's magnetic field (Correct answer)
- The compass deviation caused by onboard metal
- The angular difference between gyro north and true north
Correct answer: The difference between true north and magnetic north due to Earth's magnetic field
Magnetic variation is the angular difference between true north (geographic) and magnetic north caused by the Earth's magnetic field, shown on a chart's compass rose.
Question 3: When plotting a running fix, what is the minimum number of LOPs required?
- One LOP advanced to a second bearing (Correct answer)
- Three simultaneous bearings
- Two simultaneous bearings
- Four bearings from different objects
Correct answer: One LOP advanced to a second bearing
A running fix uses one LOP advanced along the course line to intersect a second LOP taken later, accounting for the vessel's movement between observations.
Question 4: A light characterized as 'Fl (3) 15s' means the light:
- Flashes once every 3 seconds for 15 total flashes
- Shows 3 flashes in a group, with the full cycle lasting 15 seconds (Correct answer)
- Flashes 3 times per second with a 15-second period
- Is a fixed light visible for 15 miles
Correct answer: Shows 3 flashes in a group, with the full cycle lasting 15 seconds
Fl (3) 15s indicates a flashing light that shows a group of 3 flashes, with the complete cycle (flashes plus eclipse) totaling 15 seconds.
Question 5: What does the abbreviation 'PA' on a nautical chart signify?
- Permanent anchorage
- Position approximate (Correct answer)
- Prohibited area
- Pilot advisory
Correct answer: Position approximate
PA (Position Approximate) on a chart indicates that the plotted position of an object or feature is not precisely determined and should be treated with caution.
Question 6: Which of the following correctly describes a 'cocked hat' in celestial navigation?
- A single precise fix from three simultaneous bearings
- A small triangle formed when three LOPs do not meet at a single point (Correct answer)
- The intersection of two LOPs corrected for compass deviation
- A bearing taken when the vessel is on a reciprocal heading
Correct answer: A small triangle formed when three LOPs do not meet at a single point
A cocked hat is the small triangle formed when three lines of position fail to intersect at a single point, indicating observational or plotting errors.
Question 7: On a NOAA nautical chart, a number printed in italics within the water area represents:
- A depth in feet below chart datum (Correct answer)
- The distance to the nearest port
- A magnetic bearing between landmarks
- A recommended speed limit in knots
Correct answer: A depth in feet below chart datum
Italic numbers on NOAA nautical charts represent water depths (soundings) in feet or meters below chart datum, typically mean lower low water (MLLW).
MMC Navigation & Charting 2
On a nautical chart, what does a blue tint in shallow water areas indicate?