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Author Topic: Photo Realignment  (Read 9003 times)

Terrence Elliott

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Photo Realignment
« on: November 23, 2013, 11:57:15 AM »
Hi

I have processed a UAV project of 1900 images - 5 of which did not align at all or aligned incorrectly (all in the same region)
I can see why they struggled to align as the texture is very similar across all these pics.

I have reset the camera alignment and selected only those images as well as 5/6 images in the region to re-align. The images seem to have re-aligned the 2nd time around however I have a question:

Do the images that I selected only re-align to one another or do they also take into account the aligned images surrounding them?

I just want to make sure that all my images are on the same system.

A follow question from this would be in the initial photo alignment - Does the software hold one particular image fixed (say in the middle) and fit everything onto that or is it a completely "free" adjustment?

Any help or info anybody has is much appreciated.

Regards

David Cockey

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Re: Photo Realignment
« Reply #1 on: November 23, 2013, 05:21:16 PM »
I have reset the alignment and then realigned a single camera and the result is correct relative to the other images. So it appears that realigned images are realigned relative to the other images in the chunk.

Terrence Elliott

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Re: Photo Realignment
« Reply #2 on: November 25, 2013, 11:37:19 AM »
Thanks for the info David.

Any ideas on my second question?

Alexey Pasumansky

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Re: Photo Realignment
« Reply #3 on: November 25, 2013, 11:44:40 AM »
Hello Terrence,

When "Align selected"  feature is run, PhotoScan uses matches found during Align Photos stage (and marker positions, if any) to estimate positions of the selected NA cameras.
Best regards,
Alexey Pasumansky,
Agisoft LLC

tommyboy

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Re: Photo Realignment
« Reply #4 on: March 04, 2014, 10:47:15 AM »
I am doing human scans, with a similar issue.  On particularly difficult subjects that have very bland clothing, I get say 10% of the cameras that won't align.  After the initial solve, I try to right-click "Align Selected Camera" on these NA cameras, and they still won't align.

Is there any other way to deal with this?  Is this one of the situations that coded targets are meant to help with specifically?  Can one load a camera XML from a previous solve, with this initial positioning being a 'suggestion' of where to start?  Could one hack the "ground control" system to allow this?

admir

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Re: Photo Realignment
« Reply #5 on: March 04, 2014, 01:31:11 PM »
I am doing human scans, with a similar issue.  On particularly difficult subjects that have very bland clothing, I get say 10% of the cameras that won't align.  After the initial solve, I try to right-click "Align Selected Camera" on these NA cameras, and they still won't align.

Is there any other way to deal with this?  Is this one of the situations that coded targets are meant to help with specifically?  Can one load a camera XML from a previous solve, with this initial positioning being a 'suggestion' of where to start?  Could one hack the "ground control" system to allow this?

Are you using masks ? In some cases when cameras won't align (i am doing human scans also), i delete masks from non-aligned photos and do realigment and it works in 90%. Another thing to try is to use Generic pair selection (in aligment stage) or Disable if you are using pair preselction.

Hope it helps,
Admir

tommyboy

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Re: Photo Realignment
« Reply #6 on: March 04, 2014, 08:51:57 PM »
Are you using masks ? In some cases when cameras won't align (i am doing human scans also), i delete masks from non-aligned photos and do realigment and it works in 90%. Another thing to try is to use Generic pair selection (in aligment stage) or Disable if you are using pair preselction.

I tried deleting the masks for the NA cameras, and the realignments still would not work.  I normally use Generic pair selection during alignment.  What do you mean specifically by pair preselection, are you specifying this via Ground Control?  I'm unaware of anywhere else to specify this type of relationship for the cameras, but it sounds very useful since our cameras are in a fixed position and pairings.  Thanks!