USCG Exam Practice · Chart symbols and abbreviations (Chart No. 1)
On a US nautical chart, soundings are referenced to which datum?
- AMean High Water (MHW)
- BMean Lower Low Water (MLLW)✓ correct
- CMean Sea Level (MSL)
- DMean Low Water (MLW)
Why B is correct
US charts reference soundings to Mean Lower Low Water (MLLW), as stated in the chart title. A mariner must verify the unit (feet, fathoms, or metres) before plotting. Bowditch Ch. 4 §403.
Cited:Bowditch Ch. 4 §403
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