USCG Exam PracticeApplying tide corrections to charted depth
You are transiting a channel at low water. The charted sounding is 12 feet and the predicted height of tide is -1 foot. Your vessel drafts 10 feet. What is your underkeel clearance?
- A. 3 feet
- B. 2 feet
- ✓ 1 footCorrect
- D. 0 feet
Why C is correct
A negative tide height means the water surface is below MLLW. Actual depth = 12 + (-1) = 11 feet. Underkeel clearance = 11 - 10 = 1 foot. Ignoring a negative tide correction would overstate available depth.
Cited:Bowditch Ch. 9 §904