USCG Exam PracticeApplying tide corrections to charted depth
A mariner obtains a tide table prediction for a reference station showing high water of +4.8 feet at 0930 local time. The subordinate station correction is -0.6 feet for height and -25 minutes for time. The vessel requires a minimum actual depth of 9 feet to transit a shoal charted at 5 feet. At what time is the earliest the vessel can safely transit, and what is the actual depth at that corrected high water?
- ✓ 0905 local time; actual depth 9.2 feetCorrect
- B. 0905 local time; actual depth 9.8 feet
- C. 0955 local time; actual depth 9.2 feet
- D. 0955 local time; actual depth 9.8 feet
Why A is correct
Corrected high water time: 0930 - 25 min = 0905. Corrected high water height: 4.8 - 0.6 = 4.2 feet. Actual depth at shoal: 5 + 4.2 = 9.2 feet, which meets the 9-foot minimum. The subordinate station corrections are applied to the reference station values per Bowditch Ch. 9 §905, and actual depth is computed per §904.