Navigation General · Light Ranges
'Bobbing a light' — deliberately raising and lowering your eye to make a light appear and disappear at the horizon — is used to:
- AIdentify the light's color
- BEstimate that you are at the light's geographic range (distance off)✓ Correct
- CMeasure the tide
- DCheck the compass
Explanation
When a light is first raised, an observer can confirm being at its geographic range by bobbing — ducking down to make it dip below the horizon and rising to bring it back. Knowing the light's geographic range then gives an approximate distance off.
Authority: Bowditch (Pub. 9); piloting
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