What is the nautical definition of the horizon?
Quick Answer: In nautical terms, the horizon is the visible line where the sky seems to meet the sea or land. It’s the limit of what you can see, used as a reference point for navigation and during nautical twilight to measure the sun’s position below this line.
The nautical horizon is a practical concept for sailors and navigators. It’s the boundary between earth and sky that you can actually see from your standpoint. This line isn’t fixed because it depends on your height above sea level and weather conditions.
During nautical twilight, the sun is between 6 and 12 degrees below this horizon. This phase is key for sailors because the horizon is still visible at sea, allowing them to take reliable navigational sightings using celestial bodies without full daylight.