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Originally Posted by Evenstar
Then why do so many power boat operators say that they have trouble seeing kayaks - when I can see them for at least a mile away? (assuming decent weather conditions - and I obviously talking about in daylight here)
There's nothing faulty about my logic - because we're talking about visibility over relatively short distances here - like a mile or less (not several miles).
BTW your figures and calculations are way off. In a sitting position my eyes are 32 inches high - not "less than 2 feet"(I'm 6 feet tall and have a long torso). So I can see a 1-foot high kayak that is just over 3 nautical miles away. And, I can see the other person in kayak up to about 4 nautical miles away - which is equal to 4.6 miles
The formula is 1.17 times the square root of your height of eye = Distance to the horizon in nautical miles. But that's just to the horizon. You have to do the same calculation (1.17 times the square root) on the height of the other object, and then you have to ADD the two together.
And speed has a great deal with the ability to see what is nearby, as you're moving too fast to see everything. If you don't believe me, try driving a section of road at like 50 MPH, and then walk a mile or two of that same section. I guarantee that you'll see things walking that you didn't notice when you were driving. You simply have more time to see all the details.
Plus, the higher you are, and the closer you are, the more that a boat like a kayak blends in with the water around it - because you are looking down on it. I'm actually sitting slightly below the waterline - so I'm looking across the water at other kayaks and and not down at them.
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I would like to see an experiment on that one... I have 20/15 vision and don't think that I could see a kayak 1' high at 3 nautical miles...At that distance it would blend in with the waves/surroundings and look quite insignificant. Your visibility formula may or may not be accurate (I did not bother to investigage but will take your word on it) but it is all relative to the size of the object that you are looking at and the overall light conditions at that time.