RYA Day Skipper Coastal Navigation & Chart Work — Questions and Answers
Question 1: On an Admiralty chart, a depth sounding shown in bold italic figures indicates:
- A drying height — the figure is the height above chart datum when dry (Correct answer)
- A depth in fathoms
- A depth that is uncertain
- A wreck
Correct answer: A drying height — the figure is the height above chart datum when dry
Bold italic soundings on a chart are drying heights — areas that dry out at low water. The figure gives the height above chart datum (CD) at which the feature dries.
Question 2: What does a purple flashing light symbol with the annotation 'Fl(3)10s15m10M' indicate on a chart?
- A light that flashes 3 times, has a period of 10 seconds, is 15 metres high, visible for 10 nautical miles (Correct answer)
- A light that is 10 seconds on and 3 seconds off at 15m height
- A light visible from 15 miles that flashes every 3 seconds
- A fixed light at 10m height visible for 15 miles
Correct answer: A light that flashes 3 times, has a period of 10 seconds, is 15 metres high, visible for 10 nautical miles
The notation is standard: Fl(3) = 3 flashes per period; 10s = period of 10 seconds; 15m = height of light above MHWS; 10M = nominal range in nautical miles.
Question 3: A skipper plots a course of 135°T. Variation is 3°W and deviation is 2°E. What is the compass course to steer?
- 134°C (Correct answer)
- 136°C
- 130°C
- 140°C
Correct answer: 134°C
True to Compass: apply variation (W = add) → 135 + 3 = 138°M; apply deviation (E = subtract from magnetic) → 138 − 2 = 136°C. Wait — error correction: T+3W = 138M, 138M−2E dev = 136°C. Correct answer: 136°C.
Question 4: What is the purpose of the 'estimated position' (EP) on a chart?
- To show the vessel's best-estimated position using course, speed, and tidal data when no fix is available (Correct answer)
- To show the last confirmed GPS fix
- To mark a waypoint
- To indicate a dangerous shoal
Correct answer: To show the vessel's best-estimated position using course, speed, and tidal data when no fix is available
An EP is derived by applying water track (course and log) and tidal stream to the last known position. It is less reliable than a fix but better than nothing.
Question 5: On a chart, a wreck is shown with a dashed outline. This indicates:
- A dangerous wreck, the depth over which is unknown or less than 20 metres (Correct answer)
- A cleared wreck safe for navigation
- A historical wreck with no navigational significance
- A submarine cable
Correct answer: A dangerous wreck, the depth over which is unknown or less than 20 metres
A wreck with a dashed outline (and often a cross) indicates a dangerous wreck. The dashed outline signals uncertainty about safe clearance depth.
Question 6: A transit bearing consists of two charted objects in line. When is it most useful for pilotage?
- To confirm you are on the correct leading line or track, as it requires no compass (Correct answer)
- To find your distance off the coast
- To measure depth
- To calculate tidal set
Correct answer: To confirm you are on the correct leading line or track, as it requires no compass
A transit (two objects in line) gives an exact position line that requires no compass or deviation error — it is the most reliable bearing for pilotage.
RYA Day Skipper Coastal Navigation & Chart Work
On an Admiralty chart, a depth sounding shown in bold italic figures indicates: