Rocky coasts and harbor entrances need fixed lights. A lighthouse is a tower or substantial structure equipped with a powerful light and often other aids, built to warn ships of hazards and to mark safe approaches.

Each lighthouse has a characteristic flash pattern and color that identify it on the chart and in the light list. Many are now automated, with remote monitoring replacing resident keepers. Some historic lighthouses remain active aids; others have been superseded by buoys or electronic systems but still stand as landmarks.

Despite GPS, lighthouses provide visual confirmation of position and a reliable signal when electronics fail. Mariners continue to take bearings on lighthouse lights as part of traditional and backup navigation practice.

• Tower or structure with a navigational light
• Marks hazards and safe approaches
• Identified by characteristic light pattern
• Still used for visual navigation and backup