Agisoft Metashape

Agisoft Metashape => General => Topic started by: Lauren_O on October 01, 2018, 07:50:50 PM

Title: Model distortion - Two Levels
Post by: Lauren_O on October 01, 2018, 07:50:50 PM

Hello,

I've run into this issue with two models now, and I'm hoping someone has experience working around it.

I'm reconstructing a scene of a house and beach in Photoscan. However, part of the model was reconstructed at a sharp downward angle from the rest of the scene, with the rest of the scene continuing at the appropriate angle (but much lower elevation) than the rest of the model.

I've attached two screenshots as an example of what I'm seeing.

Has anyone seen this kind of distortion before, and do you have experience with fixing it?

Thank you!

Title: Re: Model distortion - Two Levels
Post by: wizprod on October 01, 2018, 08:40:47 PM

Are the GCP’s using GNSS coordinates?
I think you need some more intermediate shots between your scenes.

Title: Re: Model distortion - Two Levels
Post by: Lauren_O on October 01, 2018, 08:55:49 PM

Yes, GCPs are from GNSS coordinates using RTK GPS.

I have what appears to be good image overlap, but is there a way to calculate % image overlap in Photoscan to identify areas that may need more photographic coverage?

I'm running the model again after updating camera alignments, so I'm hoping this helps.

Title: Re: Model distortion - Two Levels
Post by: wizprod on October 02, 2018, 07:46:57 AM

Try running the alignment again without reference preselection, and If that also doesnt produce a uniform cloud as well, you could also try without the generic preselection enabled as well.
Processing times will rise dramatically, but if it gets you a better model, I guess it is a small price to pay.

Title: Re: Model distortion - Two Levels
Post by: Alexey Pasumansky on October 02, 2018, 02:06:38 PM

Hello Lauren_O,

If the problem persists, please send the project saved after the alignment operation to support@agisoft.com, so that we could try to check what's happening. (just save as PSZ file to have a single-file project).

Title: Re: Model distortion - Two Levels
Post by: Lauren_O on October 04, 2018, 12:13:41 AM

Thank you wizprod and Alexey.

Wizprod, I'll try your suggestions this afternoon. I've tried rerunning the image alignment several different ways now, and I'm still running into that problem.

Alexy, I'll go ahead and send the file to Agisoft support as well. Will I need to attach images to the file as well?

Title: Re: Model distortion - Two Levels
Post by: Alexey Pasumansky on October 06, 2018, 10:16:57 PM

Hello Lauren_O,

I've sent a reply to your e-mail.

In brief I'll also post here for others who may be experiencing similar problems: since the project contains the oblique images I recommend to uncheck all cameras in the Reference pane prior to the alignment and do not use Reference pre-selection, as it could lead to the loss of valid pairs during matching. Unchecking cameras would disable the utilization of the camera coordinate/orientation information during the alignment and it could be helpful due to the possible issues with the DJI altitude data and orientation angles.
Also use High accuracy for the alignment.

In the bigger chunk from the project I have managed to align the images in two blocks (227 and 395 images in each), but they fail to align in the single block basing on the matching points available in the project. I assume that it could be caused by Low accuracy used and Reference preselection.