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), which represents the lowest average low tide and therefore provides the most conservative (shallowest) depth reference for navigation. The sounding unit is stated in the chart title. (Bowditch Ch. 4 §403)
Cited:Bowditch Ch. 4 §403
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