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<blockquote data-quote="Pbartender" data-source="post: 5217225" data-attributes="member: 7533">Largely, it'll depend on how good the eyesight of the observer is.&nbsp; Very often an object may be visible, even though fine details cannot be resolved.However, what you seem to be looking for is the effective horizon distance, and how that is affected by tall objects.&nbsp; <a href="http://en.wikipedia.org/wiki/Horizon" target="_blank">Wikipedia has a decent article</a> on it, with all the relevant formulas, should you want to get that detailed.Basically, the formula is roughly d=√1.5h.&nbsp; Where d is the distance that can be seen (horizon) in miles, and h is the height of the eyes of the observer in feet.So, a 5' 7&quot; tall person has a horizon of about 2.9 miles on level ground.&nbsp; At the top of a 100 foot tall tower, you'd have a horizon of 12.25 miles.&nbsp; At the top of a mountain a half mile high, you'd be able to see nearly 63 miles on a clear day.When looking at something tall from something tall, you add the two together.&nbsp;&nbsp; So, a 5' 7&quot; tall person on level ground could see the tippy-top of a 100' tall tower from a little more than 15 miles away.&nbsp; Someone in the tower could also see that 5' 7&quot; person from the same distance, presuming they had good enough eyesight to distinguish something that small from that far away.</blockquote>

[QUOTE="Pbartender, post: 5217225, member: 7533"] Largely, it'll depend on how good the eyesight of the observer is. Very often an object may be visible, even though fine details cannot be resolved. However, what you seem to be looking for is the effective horizon distance, and how that is affected by tall objects. [url=http://en.wikipedia.org/wiki/Horizon]Wikipedia has a decent article[/url] on it, with all the relevant formulas, should you want to get that detailed. Basically, the formula is roughly d=√1.5h. Where d is the distance that can be seen (horizon) in miles, and h is the height of the eyes of the observer in feet. So, a 5' 7" tall person has a horizon of about 2.9 miles on level ground. At the top of a 100 foot tall tower, you'd have a horizon of 12.25 miles. At the top of a mountain a half mile high, you'd be able to see nearly 63 miles on a clear day. When looking at something tall from something tall, you add the two together. So, a 5' 7" tall person on level ground could see the tippy-top of a 100' tall tower from a little more than 15 miles away. Someone in the tower could also see that 5' 7" person from the same distance, presuming they had good enough eyesight to distinguish something that small from that far away. [/QUOTE]

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