Chart Navigation & Plotting · Set & Drift — Head Current
To make good 10 knots SOA against a 2-knot head current, the speed through the water must be:
- A10 knots
- B8 knots
- C12 knots✓ Correct
- D5 knots
Explanation
A head current subtracts from speed over ground: STW − 2 = 10, so STW = 12 knots.
Authority: Bowditch (Pub. No. 9), Current Sailing
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