Chart Navigation & Plotting · Tides — Vertical Clearance
A bridge shows a charted vertical clearance of 55 ft above mean high water. At a moment when the tide is 3 ft below mean high water, what is the actual clearance available?
- A58 feet✓ Correct
- B52 feet
- C55 feet
- D49 feet
Explanation
Charted vertical clearances are referenced to mean high water. When the water level is 3 ft below MHW, the available clearance increases by 3 ft: 55 + 3 = 58 ft. Lower water gives more overhead clearance.
Authority: NOAA charts; Bowditch (Pub. No. 9), vertical clearances
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