USCG Exam PracticeChart symbols and abbreviations (Chart No. 1)
On a US nautical chart, soundings are referenced to which datum?
- A. Mean Sea Level (MSL)
- ✓ Mean Lower Low Water (MLLW)Correct
- C. Mean High Water (MHW)
- D. Mean Low Water (MLW)
Why B is correct
US charts reference soundings to Mean Lower Low Water (MLLW), which represents the lowest average tide level and therefore provides the most conservative (shallowest) depth reference for navigation. The sounding unit is stated in the chart title.
Cited:Bowditch Ch. 4 §403