How Far Can You See at Sea?( offshore oil drilling )

Where our line of sight hits the horizon is the distance from our boat to the horizon. A small boat first coming into view is assumed to be at that distance. In the picture above, the sailor cannot see the island's palm trees.

If an object, such as a large ship or a palm tree on an island, sticks up well above the water, we can see it from a further distance.

First let's assume that we are sitting in the cockpit of the boat and our eyes are 5 feet above the water and the seas are smooth. We can then look at the table below to see that we can see only 2.6 nautical miles to the horizon.

Now if we are looking at a palm tree on an island, we must determine how far the palm tree can see, or really how far someone on top of the palm tree can see. Let's assume the palm tree is 30 feet tall. Looking at the table, we can see the sight distance is 6.4 nm. To determine how far that palm tree is from our boat, when we first see it, we add our sight distance, 2.6 nm, to the "tree's sight distance", 6.4 nm, and find that we can see the palm tree from 9 nautical miles. This of course assumes no fog, rain, or other conditions that might obscure our view.

In case you were wondering about other heights, like when the deck of your boat is 4 feet over the water and your eye is another 4 feet over the deck, here is the calculation for finding sight distacne for any height.

Try a few other combinations. For example, how far away could you be and see the first offshore oil rigs in the Gulf of Mexico?

Rush 24/7 on August 5, 2008

".... Our buddies, our buddies at CNN, they're preparing a retrospective special, ladies and gentlemen, on the disaster that was the oil spill at Prince William Sound or the Exxon Valdez. What they will not tell you is that if you go up there today, you won't find any evidence of it, other than the stupid memorials that human beings built.

"This is where oil was on the rock. This is where the otter got eaten by the shark when we threw it back in there, and the sea lion or whatever ate the otter." Nature cleaned up itself so damn fast. It was such a laughable thing to watch people with dishtowels and Dawn dishwashing detergent wiping oil off of the rocks at Prince William Sound. Oh, it was an unpleasant sight. Of course, the birds got oil on their wings, and it was not pleasant to look at, but it's an accident. The skipper of the Exxon Valdez did not say, "I want to destroy America! I want to destroy Alaska," and then let the stuff go. But anyway, the sea eats oil. The sea eats oil alive. That place up there, nature cleaned it up faster than we ever could. Why in the world this abject hatred for a commodity? I mean, I can understand if you're a little kid, and you don't like peas or broccoli, but an entire political party and an ideological movement has now targeted oil as as big a threat to this country as conservative Republicans are! It's hard to get your arms around it."

The equation is this: Visible distance (nautical miles) = 1.17 × Square root
of the height (feet)

What that means is that an oil derrick 100 feet tall would be entirely below the
horizon at 11.7 nautical miles (13.5 statute miles) from shore. (Multiply
nautical miles by 1.15 to get statute miles.) If painted sea green/blue, they’d
be invisible even closer.

A 400-foot wind turbine would be entirely below the horizon at 23.4 nautical
miles (26.9 statute miles) from the Kennedy clan’s retreat on Cape Cod.

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