Chart Navigation & Plotting · Tides — Vertical Clearance
A bridge shows a charted vertical clearance of 65 feet (referenced to MHW). At your time of passage the tide is 3 feet below MHW. What vertical clearance is actually available?
- A62 feet
- B68 feet✓ Correct
- C65 feet
- D3 feet
Explanation
Charted vertical clearances are referenced to mean high water, the conservative (least-clearance) datum. When the tide is below MHW, more clearance is available: 65 ft + 3 ft = 68 ft. When the tide is above MHW, clearance is reduced.
Authority: Bowditch (Pub. No. 9); Chart No. 1
Practice the full Chart Navigation & Plotting bank
Free spaced-repetition quizzing across 2190 USCG exam questions — it schedules your reviews so the ones you miss come back until they stick.
Related Chart Navigation & Plotting questions
- Tides — Vertical Clearance
A bridge shows a charted vertical clearance of 65 ft (referenced to mean high water). At a state of tide 4 ft below MHW, the available clearance is:
- 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?
- Chart Basics
On a Mercator chart, one nautical mile is measured using the:
- Chart Basics
The principal advantage of the Mercator projection for navigation is that:
- Chart Basics
Charted depths (soundings) on a U.S. chart are referenced to which tidal datum?
- Chart Basics
Vertical clearances of bridges and overhead cables on a U.S. chart are normally referenced to: