USCG Exam PracticeChart symbols and abbreviations (Chart No. 1)
A mariner notes that a lighthouse symbol on a chart uses a star as its position symbol, while a nearby buoy uses a small circle. The vessel needs the precise charted position of each aid for a danger-bearing calculation. Which statement correctly describes how to extract those positions?
- A. The position of the lighthouse is the outermost point of the star; the position of the buoy is the outermost point of the circle.
- ✓ The position of the lighthouse is the centre of the star; the position of the buoy is the centre of the circle.Correct
- C. The position of the lighthouse is the centre of the star; the position of the buoy is the anchor point at the base of the circle.
- D. Both aids use the geometric centroid of their respective symbols, but only the buoy position is considered precise.
Why B is correct
For both symbol types, the precise charted position is the centre of the symbol — the centre of the star for a lighthouse and the centre of the small circle for a buoy. Using any other reference point on the symbol will introduce positional error into danger-bearing or clearing-bearing calculations. (Light List — Position Symbol)