Lighthouse

A tower or other structure that displays a conspicuous light to guide ships and warn them of hazards. Its location and light pattern help mariners identify it.

Fresnel lens: A lens made of concentric sections that focuses light while using less material than a conventional lens. Its compact design concentrates a lighthouse lamp into a beam visible over long distances.
Maritime navigation: The practice of planning and controlling a vessel's movement across water. Lighthouses are fixed aids within the wider practice of navigating at sea.
Pharos of Alexandria: An ancient lighthouse built on the island of Pharos at Alexandria in Egypt. It became the most famous ancient model of a purpose-built lighthouse.
Harbor light: A navigational light marking a harbor entrance or nearby channel. Harbor lights guide vessels through the final approach to sheltered water.
Lighthouse automation: The replacement of routine human lighthouse operation with automated equipment and remote monitoring. Automation ended the keeper's role at many lighthouses while preserving their signals.
Occulting light: A navigational light whose periods of darkness are shorter than its periods of light. Its timed flashes distinguish one lighthouse from nearby lights.
Navigational aid: A device, structure, or system that helps vessels determine position, course, or hazards. A lighthouse is one kind of fixed visual aid to navigation.
Ancient Alexandria: A major ancient Mediterranean city founded by Alexander the Great in Egypt. Its busy harbor created a need for the Pharos lighthouse.
Range lights: A pair of aligned lights used to indicate a safe course through a channel. Together, range lights can guide a vessel where a single lighthouse cannot.
Trinity House: A British corporation responsible for maritime safety, including aids to navigation around England, Wales, and the Channel Islands. It shaped the provision and management of lighthouses in British waters.

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