Some member have questioned my image as whether it is totally flat.
I have the same question too. If the plane's wingspan is
not flat against the plane of camera, it's wingspan will be
less than its actual value, and when I use smaller wingspan value as a reference to figure out the length of the body, it will give a
longer body length estimate than the actual value.
The way to check that is to draw a horizontal line across the body and thus divide the body into two halves. And if the wingspan is
totally flat against the camera, then the wingspan of the two halves should be
equal.
If the nose of the plane tilts either toward or away from the camera, it will have a shorter length than the actual value. The longest length value is when the length of the body is flat against the camera.
Here, this is what I did.
1.) The satellite image gave an estimate of
14.0m wingspan for J-20.
2.) So I resize the ruler until the
7 mark falls exactly within the two red lines of the top half of the body.
3.) Then, I copy the ruler, and place it on the lower half of the wing, and it falls exactly on the
7.1 mark.
4.) So, the two halves of the wing, has a
1cm difference, which indicates the wingspan of J-20 in the image
is
almost flat against the camera.
5.) Most people here at PDF believe J-20's overall length is only
20.35 meters as obtained from the blurry satellite picture. And I have calculated the overall length of the J-20 LRIP bird as actually
23.06 meters.
6.) Will this
1 cm difference in wingspan, cause a
2.71 meters difference, in the overall length of the J-20? I really don't think so.
In the image below, I used a measuring tape to measure the overall length and wingspan of J-20, then compute their ratio and multiply it by 14.0, which is the wingspan.
The J-20 LRIP version has a tailboom that is 30cm longer than the version 2001.