Chart Navigation & Plotting · Piloting — Geographic Range
A light is charted at a height of 225 feet and your height of eye is 36 feet. Using 1.17 × √height (feet) for each, what is the geographic range at which you would expect to first raise the light?
- A21.0 nautical miles
- B17.6 nautical miles
- C24.6 nautical miles✓ Correct
- D30.1 nautical miles
Explanation
Geographic range = 1.17(√225 + √36) = 1.17(15 + 6) = 1.17 × 21 ≈ 24.6 nm. Geographic range depends only on the heights of the light and the observer's eye, independent of the light's candlepower.
Authority: Bowditch (Pub. No. 9), geographic range; NGA Light List
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