Two lights associated to form a range which often, but not necessarily, indicates a channel centerline. The front range light is the lower of the two, and nearer to the mariner using the range. The rear range light is higher and further from the mariner.
A pair of lighthouses which indicate a safe course when lined up one above the other. Sometimes one or both may be simple skeleton towers but older range lights can often be fine heritage structures. Example: Leards Range, PEI (front & rear).
Two lights or Day-Marks, located a distance apart, visible from one direction only. When one light is visible directly above the other, you are in the marked channel for safe passage.
used by mariners to fix their position in open water and guide them into port. Range lights usually appear in pairs and are 1000 feet apart.
A set of two small lighthouses, aligned so that if a vessel lines them up, they will be guided safely into a harbour, through narrow channels.
Two lights, located some distance apart, visible in one direction only. When a ship is steered so that one light is directly above the other, they will be in the marked channel.
Pairs of fixed aids that are typically used to guide ships into or through channels; the lights are typically defined by upper and lower positions; when the lights are aligned as described in the USCG light list, the mariner will know his position relative to the channel.