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 On 21 Mar 2010, at 8:30 AM, ADavidhazy wrote: > Hi, I received the following inquiry or request for assistance. I think this is > something > valid to consider. There are several approaches to the solution. If you were > asked this > question how would you answer? Several faculty members at RIT could not answer > this though!! > > ----------------------- begin ------------------------- > > I'm working on a story about the proposal by the NY Power Authority to build > wind farms in Lake > Ontario and Lake Erie. What I want to do is produce a photograph, or series of > them, showing how the > view from the shoreline would change if 400-foot-tall turbines were erected in > the lake. > > We'd Photoshop-in the turbines (with proper disclaimers), but want the image > to be as accurate as > possible. I'm wondering if you might might help us. We need to know how "big" > to make the turbine > appear in the photo. Any thoughts would be helpful. Thanks. > > ----------------------- end ------------------------- > > What is needed is a step-by-step guide that anyone who by their self admission > is math phobic. I may reveal my answer(s) if anyone is interested. andy > Roger Eichhorn Professor Emeritus University of Houston eichhorn@xxxxxx
