Been following this thread and am not sure what the person is asking.
The simple formula for the distance to the horizon is: Take the Square Root
of your height in feet and multiply that by 1.23 and that is the number of
miles to the horizon. Square Root of 400 feet is 20, times 1.23 = 24.6
miles. If the turbines are "in" the lakes, how much is submerged? What is
the size (diameter) of the turbine blades? I'm confused. :-)
Walter Mayes
Subject: Re: How tall should the turbines be?
Correct. From the same formula, one can calculate that an observer at 200
ft above the surface would see the "base" of the turbine at a distance of
30.2 miles, therefore all of it. The tip would disappear at a additional
distance of 42.6 miles, or 72.8 miles in total.
Roger
On 21 Mar 2010, at 2:35 PM, Rich Mason wrote:
Don't forget to factor in the height of the observer's position. It's
one thing to be at lake level, another to be 200 feet up on a bluff.
Rich
On Mar 21, 2010, at 12:38 PM, Roger Eichhorn wrote:
Andy,
The tip of the turbine should disappear from view when it is located a
distance, along the circumference of the earth, c (away from the
observer), equal to the radius of the the earth, r, times the arcos of
the ratio of the radius of the earth divided by the radius plus the
height of the turbine, where the angle implied is measured in radians.
Taking r = 12,000 miles, this gives c = 42.6 miles for an object 400 ft
tall. The apparent height should be approximately equal to the actual
distance away divided by c times 400, in feet. So, a turbine located
21.3 miles away should appear to be 200 ft tall. I haven't worked out
how this translates to image size, focal length, etc.
Roger
Roger Eichhorn
Professor Emeritus
University of Houston
eichhorn@xxxxxx
