OBS Navigation & Route Planning 3 — Questions and Answers
Question 1: What does a flashing yellow light on a buoy typically indicate?
- A danger or hazard area requiring caution (Correct answer)
- A safe water mark at the center of a channel
- A dredging operation in progress
- A fish haven below the surface
Correct answer: A danger or hazard area requiring caution
Flashing yellow lights mark caution areas, such as traffic separation zones or areas requiring special attention.
Question 2: A nautical chart shows a depth of 15 feet at Mean Lower Low Water (MLLW). What does this mean for your planning?
- The depth will never be less than 15 feet (Correct answer)
- The actual depth could be less than 15 feet during extreme low tides
- The depth is measured from the surface at high tide
- 15 feet is the average depth regardless of tides
Correct answer: The depth will never be less than 15 feet
MLLW is the charted datum (reference level), so actual depths are at or above the charted figure under normal conditions.
Question 3: When using a paper chart, what tool is used to measure distances?
- A parallel ruler
- Dividers or a compass (Correct answer)
- A protractor
- A tide table
Correct answer: Dividers or a compass
Dividers are used to measure distances on a chart by comparing the spread against the latitude scale on the chart's border.
Question 4: What is a 'range' in coastal navigation?
- The maximum distance a vessel can travel on a full tank
- Two objects aligned to indicate a safe navigational track (Correct answer)
- The width of a charted shipping channel
- The rated visibility of a navigational light
Correct answer: Two objects aligned to indicate a safe navigational track
A range consists of two fixed markers that, when aligned, guide a vessel safely along a specific track or into a channel.
Question 5: What is 'dead reckoning' navigation?
- Navigating solely by landmarks on shore
- Estimating current position using last known position, speed, heading, and time (Correct answer)
- Using a depth finder to avoid shallow water
- Calculating position using three GPS satellites
Correct answer: Estimating current position using last known position, speed, heading, and time
Dead reckoning calculates an estimated present position from a known past position, accounting for speed, direction, and elapsed time.
Question 6: You are operating in fog and hear one prolonged blast every two minutes from another vessel. What type of vessel is signaling?
- A vessel aground
- A power-driven vessel making way through the water (Correct answer)
- A sailing vessel underway
- A vessel at anchor
Correct answer: A power-driven vessel making way through the water
A power-driven vessel making way through the water in restricted visibility sounds one prolonged blast at intervals of not more than two minutes.
Question 7: On a nautical chart, magenta (pink/purple) coloring is used to indicate:
- Shallow water danger zones
- Aids to navigation, restricted areas, and important caution notes (Correct answer)
- International boundary lines
- Areas with strong tidal currents
Correct answer: Aids to navigation, restricted areas, and important caution notes
Magenta on nautical charts highlights lights, restricted areas, traffic separation schemes, and other important navigational information.
OBS Navigation & Route Planning 3
What does a flashing yellow light on a buoy typically indicate?