Identifying Lighthouses by Their Flash Patterns
Each lighthouse has a unique flash pattern (its fingerprint). Time the flashes, look up the pattern in nautical charts or apps like Navionics. Patterns prevent confusion between nearby lighthouses.
Every lighthouse has a unique light characteristic — a specific pattern of flashes, intervals, and colors that serves as its fingerprint. This pattern is published in nautical charts and can be used to identify any lighthouse you can see. How to identify a lighthouse: 1. Time the flash pattern: count seconds between flashes, note the number of flashes per cycle 2. Look up the pattern in marine navigation apps (Navionics, C-Map) or the List of Lights publication 3. Cross-reference with your approximate position Common pattern types: - Fl (flashing): single flash at regular intervals - Fl(2): two flashes per cycle - Fl(3): three flashes per cycle - Oc (occulting): steady light with regular dark periods - Iso (isophase): equal light and dark periods The system exists because before GPS, sailors needed to confirm their position by identifying specific lighthouses. Each lighthouse in a region has a deliberately different pattern to prevent confusion. Some lighthouses also use colored sectors — red, white, and green light visible from different angles — to indicate safe channels versus hazardous areas.