Hugin stitching aerial images

[David H]

I am having trouble aligning 1950's aerial images in Hugin. So far Hugin is the best option and has worked very well except it seems that when the images are stitched, they are not oriented at the angle that they should align. Most of the images I am working with align perpendicular which Hugin seems to like, but for the images that overlap at a different angle, it just defaults to a 90 degree intersection. I was trying to mess around in the parameters in the optimizer tab but nothing was working other than resulting in the images being warped. 

Because I am going to give the final stitched image geographic coordinates later on, I really want to avoid any warping in Hugin. So I'm just wanting the images to be realigned and rotated so that they overlap nicely.

The screenshot below is the output from Hugin overlaid on top of the aerial flyover index for reference. The part of the image on the far bottom right should be rotated and line up to the line that says 147. The result I want is a slight difference, but very important for the georeferencing process. Any help would be much appreciated!

I have put an example below of the result I am looking for, which I found in an academic paper.

[John Fine]

On Sun, Jul 24, 2022 at 5:13 PM David H <dave...@gmail.com> wrote:

 it just defaults to a 90 degree intersection. I was trying to mess around in the parameters in the optimizer tab but nothing was working

It wouldn't normally default to 90 degrees.  That sounds like something you would need to force by turning off optimization of "roll".

It is hard to guess what is going on without seeing the project.  I'm sure it could be fixed using just the images, but maybe there is a better way:

 

The screenshot below is the output from Hugin overlaid on top of the aerial flyover index for reference

I think you are saying you have an accurate graphic reference that (within the projection you want) is not warped.

I would include the reference as an image in the project and manually (since it is too different an image format) place control points between the actual images and the reference, so optimize can do the correct computation, then drop the reference out (either entirely or by masking) so it has guided the result without becoming part of the result.

[Carl Ovenschotel]

I have been wanting to stitch aerial images for a long time but never succeeded. But I guess it's not possible to stitch them because of parallax
mistakes in the pictures. In your project it's probably a different issue.

[johnfi...@gmail.com]

On Monday, July 25, 2022 at 2:29:46 AM UTC-4 koga...@gmail.com wrote:

I have been wanting to stitch aerial images for a long time but never succeeded. But I guess it's not possible to stitch them because of parallax
mistakes in the pictures.

I would expect aerial images of mountains would be impossible to stitch correctly because of parallax problems.

But if the surface photographed is relatively flat (vs. the altitude from which it is photographed) there should be a correct way to stitch.

Someone who understands Hugin's stitching  better than I do my correct me on this, but so far as I understand:

When the camera position is moved between images, you need some model of the target surface in order to remap the images.  Hugin can model the target as a flat surface at an arbitrary angle relative to its viewing angle from the camera position.  Given a decent collection of control points, optimization can find the position of the camera and the viewing angle of the camera (yaw, pitch and roll) AND also compute the angle of the target surface.

If the altitude of the camera is great enough relative to the surface texture, that computation should remove parallax issues.

[Terry Duell]

On Sun, 2022-07-24 at 14:07 -0700, David H wrote:
> I am having trouble aligning 1950's aerial images in Hugin.

Are you attempting to stitch using mosaic mode?
I think that would be the approach to use.

Cheers,
--
Terry Duell <tdu...@iinet.net.au>