Chart Work and Pilotage Flashcards

What datum is used for soundings on US nautical charts?

Answer: Mean Lower Low Water (MLLW)

US nautical charts use Mean Lower Low Water (MLLW) as the chart datum for soundings, providing a conservative safety reference.

What does blue tinting on a nautical chart typically indicate?

Answer: Shallow water less than the specified depth contour

Blue tinting marks shallow water areas on nautical charts, warning mariners of potentially hazardous depths.

What does the abbreviation 'PA' printed next to a chart symbol mean?

Answer: Position Approximate

PA stands for Position Approximate, indicating the charted feature's location has not been precisely surveyed.

On a nautical chart, a magenta circle with a dot in the center represents what type of navigational aid?

Answer: A fixed light structure such as a lighthouse

A magenta circle with a central dot indicates a fixed light structure on a nautical chart, such as a lighthouse or light tower.

Which statement correctly describes a large-scale nautical chart?

Answer: It shows a small geographic area with greater detail

Large-scale charts (e.g., 1:10,000) depict a smaller geographic area with greater detail, making them ideal for harbor and coastal navigation.

What does the abbreviation 'ED' following a sounding on a nautical chart indicate?

Answer: Existence Doubtful

ED stands for Existence Doubtful, meaning the charted feature may not actually exist or its position cannot be verified.

What is the purpose of a 'cautionary note' printed on a nautical chart?

Answer: To warn mariners of specific navigational hazards or restrictions

Cautionary notes alert mariners to specific hazards, regulated areas, or conditions requiring special attention that cannot be shown by standard symbols alone.