J-20 5th Gen Fighter Thread VI

[plawolf]

The issues seems to be less about points and lines and more about plains.

The virticle stablizers are on a higher plain compared to the nose for example, that’s where the triangles come into play, since the points (nose and vert tip) form an angle to the ground and thus create the triangle different-distances scenario pointed out before.

You can still get a measurement distortion from the length of something on the same plain from a viewing angle different, for example, a pen might look shorter if it is far away compared to something of the same length that is right at your feet, but the tiny distance and angular different between the J20 and J16 makes that immaterial. You would get a bigger difference from missing a pixel.

 

[taxiya]

They're not parallel. The J-20 is directly under the drone while the line of sight to the J-16 is slanted at ~20 degrees.

so long as the center line of J-20 and J-16 remains parralle and on the same plain, the position of the drone camera does not matter. It is the same principle as in #1089 I know how to demonstrate that, but I don't have 3D modelling program to do it.

 

[taxiya]

The issues seems to be less about points and lines and more about plains.

The virticle stablizers are on a higher plain compared to the nose for example, that’s where the triangles come into play, since the points (nose and vert tip) form an angle to the ground and thus create the triangle different-distances scenario pointed out before.

You can still get a measurement distortion from the length of something on the same plain from a viewing angle different, for example, a pen might look shorter if it is far away compared to something of the same length that is right at your feet, but the tiny distance and angular different between the J20 and J16 makes that immaterial. You would get a bigger difference from missing a pixel.

That is right, so long as all lines and points remain in the same plain, regardless the direction of the lines, the proportion remains constant, even if the lines have arbitrary angles between each other.

And from that proportion, plus the known factor, we can get the measure of the unknown.

 

[jobjed]

so long as the center line of J-20 and J-16 remains parralle and on the same plain, the position of the drone camera does not matter. It is the same principle as in #1089 I know how to demonstrate that, but I don't have 3D modelling program to do it.

We are taking the J-16's distorted red length as 21.935m and comparing that to the undistorted J-20. The distorted length of the J-16 is shorter than the actual 21.935m so the calculated J-20 length would, in reality, be shorter than the 21.88m people are getting.

 

[taxiya]

We are taking the J-16's distorted red length as 21.935m and comparing that to the undistorted J-20. The distorted length of the J-16 is shorter than the actual 21.935m so the calculated J-20 length would, in reality, be shorter than the 21.88m people are getting.

By looking at this demo, I think I know what you are saying now.

 

[latenlazy]

We are taking the J-16's distorted red length as 21.935m and comparing that to the undistorted J-20. The distorted length of the J-16 is shorter than the actual 21.935m so the calculated J-20 length would, in reality, be shorter than the 21.88m people are getting.

20.8*. People who are getting over 21 meters, I suspect, aren’t exacting a lot of care in where they pick the nose and tails of either plane. That said, I agree with you that there is visible distortion and that it can skew the real length ratios between the two planes, but you have to also ask just how significantly does the distortion alter the results? If the actual amount is not much, it’s not going to drastically change the results.

 

[jobjed]

20.8*. People who are getting over 21 meters, I suspect, aren’t exacting a lot of care in where they pick the nose and tails of either plane. That said, I agree with you that there is visible distortion and that it can skew the real length ratios between the two planes, but you have to also ask just how significantly does the distortion alter the results? If the actual amount is not much, it’s not going to drastically change the results.

Oh ye, brainfarted there.

20.88m was intended.

 

[taxiya]

We are taking the J-16's distorted red length as 21.935m and comparing that to the undistorted J-20. The distorted length of the J-16 is shorter than the actual 21.935m so the calculated J-20 length would, in reality, be shorter than the 21.88m people are getting.

To admit, I wrongly assumed the J-16 was one on the top side next to the J-20 with the drone above the middle of them. In that case, the relative length is not distorted.

But as you demonstrated here, you are saying the J-16 is the one on the right side of J-20 and the drone is right above J-20. I agree that there is a distortion and the closer the drone to the ground, the more the distortion. The distortion has to be removed by taking the drone's flying height into consideration which we don't have.

It is similar to how one look at the railway tracks. When looking towards the centerline between the two tracks, the further away the narrower the tracks seem to be. But when looking from the side, the width remains the same.

 

[duncanidaho]

I hope it works, it is the first time I post an image.

Please, Log in or Register to view URLs content!

The two sheets of paper in the image are of the same size, as you can see, the sheet of paper on bottom (position of the camera) is longer than the sheet of paper on top. Imagine now the bottom one is the J-20 and the top one is the J-16.

Of course the differerence of length is related to height of the position of the camera.

As you can see it in the picture of the J-20s and J-16s, the discrepance of how much the vertical stabilizer are showing backward, I think the difference is not neglectable, so therefore the J-16 looks shorter than it is.

 

[Julio Ramos]

Can't we compare sizes knowing the diameter of the engines?
We know what kind of engines both planes uses, let's use the known diameter of them to made our calculations.