What are lighthouses used for?

Answer 1

To guide ships in the water. They light up the surface so that ships do not run into rock or other boats. It reduces the chances of a crash.

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To guide shipping YES. To "light up the surface..." NO.

A lighthouse indicates the location of a headland, shoal or other hazard, or the entrance to a complex channel, and the pattern of its flashing serves to identify the location.

Answer 2

In the days before the widespread use of electronic navigation - that is to say, any time before about 1970 - lighthouses were used as visual navigational beacons to aid ships coming in to port, and to warn the sailors of obstructions.

Every lighthouse has its own "characteristics"; the speed at which the light spins, the color of the light, and the number of elements in the beam. This enables the sailor to identify a particular lighthouse, and if there are two lighthouses visible at the same time, the navigator can get a visual "fix" of his position.

Now everyone uses GPS, which is capable of even greater precision than obtaining visual bearings to three lighthouses.