USCG Exam PracticeApplying tide corrections to charted depth
The heights of bridges and navigational lights on US charts are referenced to which datum?
- A. Mean Lower Low Water (MLLW)
- B. Mean Sea Level (MSL)
- ✓ Mean High Water (MHW)Correct
- D. Mean Low Water (MLW)
Why C is correct
Heights of features such as bridges and lights are referenced to Mean High Water (MHW), not MLLW. As a result, vertical clearance under a bridge decreases as the tide rises above MHW and increases as it falls below. (Bowditch Ch. 9 §904)
Cited:Bowditch Ch. 9 §904