USCG Exam PracticeChart symbols and abbreviations (Chart No. 1)
On a US nautical chart, the clearance figure shown above a bridge symbol is referenced to which tidal datum?
- 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 clearance figures for bridges and power lines are referenced to either Mean High Water or High Water Spring depending on the specific chart, giving the mariner the least available vertical clearance. The sounding datum MLLW applies to depth figures, not overhead clearances. (Light List — Overhead Clearance)