USCG Exam PracticeChart symbols and abbreviations (Chart No. 1)
A bridge clearance of 65 feet is shown on a US nautical chart. To what tidal datum is this clearance referenced?
- A. Mean Lower Low Water (MLLW)
- B. Mean Sea Level (MSL)
- ✓ Mean High Water (MHW) or High Water Spring, depending on the chartCorrect
- D. Mean Low Water (MLW)
Why C is correct
Overhead clearances for bridges and power lines are referenced to either Mean High Water or High Water Spring depending on the specific chart, not to MLLW. This provides the most conservative (least) vertical clearance available to the mariner.