Sunday, August 16, 2009

Scanning the horizon at the beach

Just returned from a week at the beach, Emerald Isle specifically, in North Carolina between Swansboro and Morehead City. Last night the air was quite clear, giving us great distance visibility. We picked out the Cape Lookout lighthouse beacon on the horizon, which raised the question how far is the horizon?

We found an online tool to help answer this question, namely,
Distance to Horizon Calculator. You plug in how many feet you are above sea level, and it calculates the distance in miles to an object that appears on the horizon. If the object is also some distance above sea level, you could just add its height to yours.

For example, if you are standing on the beach, about six feet above the water, an object just on the horizon would be about three miles away. As we sat on the porch of the place we were staying in, about 50 feet above sea level, we could see about 9 miles to the horizon. The Cape Lookout lighthouse, with its rotating beacon 150 feet above sea level, appeared to be on the horizon from our porch location 50 above sea level, suggesting it was about 17 miles away. This estimate matches that made using a map of the area.

It was interesting to watch the ocean change during the week as the weather changed from very windy and bright to calm and cloudy, with lots of other combinations in between, including lightning, thunder, and lots of rain. But you know what they say about a rainy day at the beach.

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