Chart Navigation & Plotting · Aids to Navigation — Nominal vs Geographic Range
A light's printed nominal range may exceed the distance at which you actually see it when:
- AThe light is still below your horizon (geographic range is less) or visibility is below the standard✓ Correct
- BThe light is white
- CYou are using radar
- DIt is daytime
Explanation
Nominal (luminous) range assumes 10 NM meteorological visibility. The light is seen only when it is also above your horizon (geographic range, set by both heights) and prevailing visibility is adequate. The limiting (smaller) of the two ranges, adjusted for visibility, governs.
Authority: Bowditch (Pub. No. 9); Light List
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