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2.2 Chart Datum and Navigational Marks

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  • Chart Datum: Chart datum is the reference level used to measure water depths on nautical charts. It represents the lowest level of water that can be expected at a specific location, considering tidal variations.
  • Depth Soundings: Soundings on nautical charts indicate water depths at specific points. They are typically measured relative to the chart datum and help mariners assess the depth of water along a route.
  • Navigational Marks: Navigational marks, including buoys, beacons, and lighthouses, are critical for safe navigation. They provide visual cues and reference points to mariners, indicating hazards, channels, and safe passages.
  • Cardinal, Lateral, and Isolated Danger Marks: Different types of navigational marks use specific colors, shapes, and light characteristics to convey information to mariners. Cardinal marks indicate safe passage relative to specific hazards, lateral marks indicate the port or starboard side of the channel, and isolated danger marks indicate isolated hazards.
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