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Q: flying at certain altitudes ( Answered 5 out of 5 stars,   7 Comments )
Subject: flying at certain altitudes
Category: Science > Earth Sciences
Asked by: bamaster-ga
List Price: $2.00
Posted: 17 Mar 2005 15:57 PST
Expires: 16 Apr 2005 16:57 PDT
Question ID: 496458
Somebody at work said you can see people on the ground in a plane
flying at 8 to 10,000 feet I say you can't, who is right?
Subject: Re: flying at certain altitudes
Answered By: omnivorous-ga on 17 Mar 2005 17:20 PST
Rated:5 out of 5 stars
Bamaster --

You won't see the people unless you're flying above terrain that's
about 2,000' away.

I've done quite a bit of aviation photography and here's a series of
shots of a tour around the Olympic Mountains in the Seattle area:

The shots taken above a nuclear submarine were taken at about 1,200'
above the water -- and see how tiny the people are in it:

This shot, above the Everett Naval Station was taken from about
2,500'and already you have trouble discerning people on the ground:

This picture was taken at about 12,000' -- only 4,000' above the rim
of Mt. St. Helens and already it's impossible to pick out people. 
There's a trail that runs to the south rim of the volcano (right side
of the picture) and you couldn't pick a person out:

In fact a pilot has a hard time seeing something as large as another
plane at a distance of 1 mile (5,280').  Aircraft will appear only if
they're extremely large or with a good contrast against the sky. 
Seeing object as large as an airplane at 2 miles or 10,000' is even
harder and picking out a person nearly impossible.

Best regards,

bamaster-ga rated this answer:5 out of 5 stars
You guys we're great!!  Thanks for all the info and for the record I
meant 8000 to 10,000 but I loved your answer! lol.  Keep up the good
work.   Rick

Subject: Re: flying at certain altitudes
From: herkdrvr-ga on 17 Mar 2005 18:29 PST
Also complicating the matter is that horizontal distance is involved
unless the subject is directly underneath the aircraft, in which case,
you won't see them!  For instance, the Mt. St. Helens shot at 4,000 ft
above the rim is actually farther away due to slant distance from the


Subject: Re: flying at certain altitudes
From: pinkfreud-ga on 17 Mar 2005 18:37 PST
Maybe there's a trick to this, if the person who told you this used
the same wording you did, "flying at 8 to 10,000 feet." Notice that
this does not necessarily mean 8,000 to 10,000 feet. It could
literally be 8 feet to 10,000 feet. Taking the lower range of this,
it's obvious that if you are flying at 8 feet above the ground, you'll
be able to see people. In fact, you'll be scaring them witless.
Subject: Re: flying at certain altitudes
From: herkdrvr-ga on 18 Mar 2005 00:08 PST
Pinkfreud--YOU ROCK!

That's great.  8-10000ft!
Subject: Re: flying at certain altitudes
From: omnivorous-ga on 18 Mar 2005 07:41 PST
Bamaster --

There was another question that I'd answered concerning visibility of
aircraft at a distance that's somewhat related:

But note that the airplanes are huge in comparison to a human being: a
Boeing 747 is 232 feet long, has a wingspan of 211 feet, and is 63
feet high.

Best regards,

Subject: Re: flying at certain altitudes
From: racecar-ga on 18 Mar 2005 12:03 PST
I think the question of whether or not a given camera can resolve
people on the ground is different from the question of whether the
human eye can do so.  After all, there are supposedly cameras on
satellites that can identify the brand of a pack of cigarettes lying
on the ground.

A person with 20/20 vision can identify a letter which subtends 5
minutes of arc ( 
The resolving power required to identify a letter is probably similar
to that required to discern a person from a rock.  If you're directly
above a person who is standing, his apparent size is about 2 feet, so
he'll subtend 5 minutes of arc when you're at an altitude of about
1400 feet.  If the person is in a more visible position, say lying
spread-eagled on the snow, his apparent size might be 6 feet, and he'd
subtend 5 minutes of arc at an altitude of 4000 feet.  Even in this
most visibility-favorable case, 8 to 10 thousand feet is too high to
pick out a person for someone with normal vision.
Subject: Re: flying at certain altitudes
From: owain-ga on 18 Mar 2005 14:44 PST
Even if the plane is at 10,000 ft, nothing to say that ground level is
at mean sea level. Easy to find lots of mountains above that height.

Subject: Re: flying at certain altitudes
From: quantumdot-ga on 30 Mar 2005 10:59 PST
What about *people* at 8k-10k feet? Say a large crowd, in a football stadium?

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