Chart Navigation & Plotting · Piloting — Horizontal Danger Angle
To stay outside a charted danger circle using two fixed objects, you measure the horizontal sextant angle between them. You remain in safe water as long as the measured angle is:
- AIncreasing as you proceed
- BGreater than the danger angle
- CExactly equal to the danger angle
- DLess than the danger angle — a larger angle means you are inside the danger circle✓ Correct
Explanation
The danger circle passes through the two objects and is tangent to the hazard. As you close the hazard the subtended horizontal angle increases. Keeping the measured angle smaller than the danger angle keeps you outside the circle in safe water.
Authority: Bowditch (Pub. No. 9), horizontal danger angle
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