USCG Exam PracticeApplying tide corrections to charted depth
You are planning a transit for a date near the first quarter moon. Compared to a transit planned near the full moon, which statement best describes the expected tidal range and its navigational significance?
- A. The range will be greater (spring tide), so minimum depths will be lower at low water.
- ✓ The range will be smaller (neap tide), so the difference between high and low water depths will be reduced.Correct
- C. The range will be greater (neap tide), so maximum depths will be higher at high water.
- D. The range will be the same because tidal range depends only on geographic location, not lunar phase.
Why B is correct
Neap tides occur near first and last quarter moon and have the smallest range. Spring tides, with the greatest range, occur near new and full moon. A smaller range means less difference between high and low water; while this reduces the risk of extreme low-water shoaling, it also limits the tidal window for deep-draft transits at high water.
Cited:Bowditch Ch. 9 §902