# The difficulty of seeing the curve of the earth from 30,000 feet

#### Captainsplattapus

##### New Member
Hi. New to this forum and just wanted to throw this up there. Just for full disclosure I'm only about 3-4 weeks old as far as this flat earth topic goes and kind of like my globe the way it is, but do have a number of questions. Could someone please throw some light on to this video taken from you tube. I know there are a number of pilots here, so there opinion would be most valuable. I'm also aware of he stature of the owner of the site that this video was taken from, in the FE argument, although I don't think that this takes anything away from the legitimacy of my query. Thank everyone.

Source: https://youtu.be/8vqf-zK3pno

#### Trailblazer

##### Moderator
Staff member
Could someone please throw some light on to this video taken from you tube. I know there are a number of pilots here, so there opinion would be most valuable. I'm also aware of he stature of the owner of the site that this video was taken from, in the FE argument, although I don't think that this takes anything away from the legitimacy of my query. Thank everyone.

Source: https://youtu.be/8vqf-zK3pno

Could you please state in your own words what the alleged problem is? Metabunk has a "no-click policy", so we should be able to understand your point without having to click on a video.
https://www.metabunk.org/metabunks-no-click-policy.t5158/

As far as I can see, the video claims that because there is no easily measurable curve on the horizon of an unlabelled photo, this proves something.

What height was the photo taken from?

What was the focal length of the camera?

What was the field of view of the image?

Only once you know the answers to those questions can you compare the observed curvature with the expected curvature on a globe.

#### Trailblazer

##### Moderator
Staff member
According to the video subtitles the photo was taken at "30 plus thousand feet" using an iphone.

An iPhone 6 has a horizontal FOV of about 63 degrees.

Putting those numbers into the curve calculator we get an expected visual curvature of 0.00756, in other words for an image 1000 pixels wide, the visible curve should be about 7 and a half pixels.

I don't know about you but I see far more fluctuation than that just from the lack of certainty of where the actual horizon is, so you can't use that picture to say there is "no curve".

You simply cannot see the curvature of the horizon from normal aircraft altitudes. You have to remember that the horizon is a flat circular plane. We only see it appear to curve from great heights because we are looking down on the circle.

#### Captainsplattapus

##### New Member
Photo taken from Around or above 30'000ft

What what height would you expect to see a curve?
This is a genuine question. I am not a "flat earther", [impolite text removed] or what ever else gets used as a label. I am genuinely looking for answers to some of the questions raised by this debate.

Last edited by a moderator:

#### Captainsplattapus

##### New Member
According to the video subtitles the photo was taken at "30 plus thousand feet" using an iphone.

An iPhone 6 has a horizontal FOV of about 63 degrees.

Putting those numbers into the curve calculator we get an expected visual curvature of 0.00756, in other words for an image 1000 pixels wide, the visible curve should be about 7 and a half pixels.

I don't know about you but I see far more fluctuation than that just from the lack of certainty of where the actual horizon is, so you can't use that picture to say there is "no curve".

You simply cannot see the curvature of the horizon from normal aircraft altitudes. You have to remember that the horizon is a flat circular plane. We only see it appear to curve from great heights because we are looking down on the circle.
OK. Thanks very much. that is of great help.

#### Henk001

##### Senior Member.
What height was the photo taken from?

What was the focal length of the camera?

What was the field of view of the image?

Only once you know the answers to those questions can you compare the observed curvature with the expected curvature on a globe.
And how much lens distortion could there have been?
It makes straight lines curved depending on which part of the picture you are. It could even make curved lines straight, convex lines concave, etc. Considering the very tiny amount of curvature you could expect here this is something to consider.

From Lynch: "visually discerning the curvature of the earth" http://www.thulescientific.com/Lynch Curvature 2008.pdf

#### Trailblazer

##### Moderator
Staff member
What what height would you expect to see a curve?
This is a genuine question. I am not a "flat earther", "[flat earth believer]" or what ever else gets used as a label. I am genuinely looking for answers to some of the questions raised by this debate.

Playing around with the curve calculator, to get a 1% curve across the field of an iPhone photo (that is, a curvature of 1 pixel per 100 pixels of photo width) you would require an altitude of about 52,500 feet:

(the "distance in miles" figure at the top is irrelevant when we are talking about the horizon, as the horizon is at a fixed distance at a given height).

To get a 2% curve you would need to be about 210,000 feet up.

Flat earth proponents often seem to confuse the curvature of the Earth's surface with the curvature of the horizon. The horizon doesn't curve, it is a flat circle. The visual appearance of the curve is purely a perspective effect caused by the fact that the circle is below you.

#### Henk001

##### Senior Member.
Photo taken from Around or above 30'000ft

What what height would you expect to see a curve?
This is a genuine question. I am not a "flat earther", [impolite text removed] or what ever else gets used as a label. I am genuinely looking for answers to some of the questions raised by this debate.
Here is a link to an instructive site:
http://walter.bislins.ch/blog/index.asp?page=Flat-Earth:+Finding+the+curvature+of+the+Earth
You can fill in height FOV etc and see what to expect

Staff member
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#### Captainsplattapus

##### New Member
Much appreciated guys. will look into it.

#### Mick West

Staff member
That's a really good tool. I have put in the parameters to roughly mimic the photo in the video (although the image in the video doesn't look like a full frame iPhone photo to me, so I suspect it may have been cropped and thus show even less curvature than this)

Walter Bislins has added some very nice recreations of various observations to that tool, I've started a dedicated thread for it.
https://www.metabunk.org/earth-curvature-simulation-by-walter-bislins.t8986/

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