Question about object height vs. visibility of object- PLEASE HELP!?

Question

This is going to sound like a very odd question, but it is for something I am writing and I would truly appreciate the help. The question is thus:

Say a person was able to fly using minimum technical apparatus (ie, not using an airplane or anything largely visible-- just an object on the person). At what height would the details of this person's figure become unclear? At what height would they stop looking like a flying person and just like a moving dot, which could be confused with, say, a bird? I had estimated about 700 feet, based on a parasailing trip I did in Mexico, in which people on the ground began to look like moving dots. (so without the parasail, we probably would have seemed likewise.)

Please help me out and I would greatly appreciate it!!!

Answer 1

Sounds like research on UFO's!

But anyway, visibility is related to many (physical) factors namely the perception of foreground-background separation (contrast), size, perceived motion, etc.

Then there are the learned factors which allow you to indirectly infer visibility e.g. the knowledge that an object is a person makes you 'recognise' it as it moves further away, before it turns to a dot.

Maybe situating your problem in a practical context would get better help?

Answer 2

It also depends on the eyesight of the person looking up, and whether he's using any optical aids (from glasses up to binocs and telescopes)

Answer 3

Visiblity is based on the contrast of the object vs the backround. The larger the contrast, the easier it is to detect it. This is why camoflage is so effective, as it blends into the backround, making it almost impossible to detect.

There are some other factors, such as the visiblity of the air.

On hazy days, the moisture in the air will scatter light, making it harder to see as the distance is increased. So its hard to say.  

So if your wearing pink hot pants on the parssail, id bet you'd be visible for at least 1500'. If you were wearing a light blue or white shorts. you'd loose sight in about 500' or less.

Answer 4

I would have to agree with Capt. Sead0nkey. While the quality of a person's eyesight is a signifigant factor, the object's color, and obstructions to vision such as haze, are signifigant factors as well.

    Aa a former weather observer, we would use dark red balloons, once released, would be be timed until they disappeared into a cloud deck, or obscuring phenomena such as snow or fog. The contrast between the balloon, and background of white, or light to medium grey colored cloud, along with the height of the cloud deck, would allow the balloon to be visible for 6 or 7 minutes to the naked eye, which allowed cloud layers to be measured up to about 2,760 to 3,220 feet above ground. The balloons were not very large, about twice the size of a basketball.