Leading lights
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Leading lights (aka Range Lights) are a pair of light beacons, used in position fixing and navigation, to indicate a safe passage for vessels entering a shallow or dangerous channel.
Lights that are separated in distance and elevation, so that when they are lined up vertically, with one behind the other, they provide a bearing.
Usually used to enter a harbor or navigate a channel.
Leading lights are a form of leading line that can be used at night.