Dear All,

I did a mapping project of a sports stadium and the  roof of the stadium was coming out very distorted. The roofs of the  other building in the entire orthomosaic were fine except for the  stadium roof. I flew it a second time alot slower and took more photos  of the stadium hoping to resolve this problem but no  luck. Could you  all kindly help me as to how to resolve this problem. Are there any  tools that I can use to solve this problem? Can it be fixed from the  software itself? Any advice on how to fly this project (height, photos, etc) to avoid the distorted roof edges. I am using Agisoft Photoscan Professional to stitch the images.

Thanks,

Greg

They all look the same. No problem seen.

Can you post a link to an original, untouched photo, can't tell much from that shot.

I can't see the issue you're describing from this photo. You can try uploading it as a file and generate a link through dropbox or Google drive

huntcool001@gma Posted at 2016-6-26 05:47
I can't see the issue you're describing from this photo. You can try uploading it as a file and gene ...

The edges of the circular roof (stadium roof) are all jagged. They did not come out straight. I will send the dropbox link

The edges of the circular roof (stadium roof) are all jagged. They did not come out straight. I will send the dropbox link

Waiting to see the hi-res photo.

Was it a hot day? Could they be heat from the roof causing light/images to distort, much like how mirages are formed?

Do you have a VIDEO footage of the same shot? If that was indeed caused by the hot surface, you would be able to see them wobble in the video.

FAS1 Posted at 2016-6-25 19:13
They all look the same. No problem seen.

Look at the edges closely. I can see what he refers to.

rodger Posted at 2016-6-26 08:35
Look at the edges closely. I can see what he refers to.

No, the edges are represented as they are. The green roofs are not symmetrical and even. One side may be even, but the others are not 'jagged', it is how the roof is and covers the seating.

FAS1 Posted at 2016-6-26 13:06
No, the edges are represented as they are. The green roofs are not symmetrical and even. One side  ...

I only see lagged edges especially on the outer edges of the large roofs.

Circle the areas y'all are finding offensive, please.

Looking at the blowup that FAS1 put in post #9 above....if you are looking at the green roof on the LEFT, the roof itself has some darker colors on the edges giving the 'appearance' that it is jagged.....is this what people are referring to?


Also, could JPEG interploation of the green edge of the roof to the dark shadow/ground next to the roof be creating this jagged visual effect?

  6°45'27.89"N    58°10'40.36"W    Providence Stadium / Guyana National Stadium

I am assuming the software is having a problem getting its bearings, and it is confusing sloped seating as flat ground etc.  As the aircraft orbits or takes an overlapping photo from another viewpoint, the same error is being applied.  This results in edges that look like torn paper.  The low roofs aren't too bad, but the taller ones show a lot of problems.  I assume it is altitude related, and something best referred to the author/publisher of the software.  Do they have an online forum somewhere?

FAS1 Posted at 2016-6-26 13:06
No, the edges are represented as they are. The green roofs are not symmetrical and even. One side  ...

The more and more I look at this photo, it really feels like a JPEG interpolation artifact.  Would love to see a RAW (non-JPEG) image of this to see if this exists in the original raw footage.

Flight Raptor Posted at 2016-6-28 01:15
The more and more I look at this photo, it really feels like a JPEG interpolation artifact.  Would ...

Look at this part of the image.  The right (red arrow) side of the roof is meant to be a straight edge.  The curved (green arrow) edge is supposed to be a nice sweeping curve.  These all show errors that make it look like hand torn paper edges.  They are way too bad to be jpeg artifacts.  Click on the image and zoom in a bit to make it obvious.  Click on my Google Earth image in post #13 to see what it is supposed to look like.

Flight Raptor Posted at 2016-6-27 08:15
The more and more I look at this photo, it really feels like a JPEG interpolation artifact.  Would ...

I agree with you, it looks like interpolation errors to me too. I think they are caused by lens parallax errors and this is why only the high roofs are distorted. I think the drone was flying to low and the software is having problems with the roof because overlapping frames are seeing different angles. One frame is seeing seats under the roof and the frame beside it does not, so the software is shifting the roof around in order to make sense of the only regular pattern, which is the seating. The lenses field of view is too wide. I would suggest redoing it at a higher altitude, so that the roof is at a lesser distance to the ground, relative to the lens. Also shoot many more frames with at least 50% overlap or better. Take your originals and crop away the outer 50% of the frame. This will leave images with less parallax distortion. It gets worse toward the edge of a wide angle image. Phantoms use consumer grade cameras with a fixed length lens (no optical zoom). Google maps achieves the sharpness by zooming in at a much higher altitude so the images practically stitch themselves together. But if you look closely at the upper left quadrant of the google image, you can see the same type of distortion between the seats and the roof. The other quadrants look good because the stitching algorithm is giving priority to the roof edge, rather than the seat pattern under it.

Thank you all for you input and advice. I will fly this again at a much higher altitude and let you all know of the results.