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Author Topic: Questions about View matches in PhotoScan  (Read 4909 times)

Rosy

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Questions about View matches in PhotoScan
« on: January 31, 2018, 12:53:35 PM »
Dear,

I've aligned some photos. In the "Photos" panel, right click "View matches". Then I see red and blue lines. What does these lines represent?

Red for fault matches and blue for correct matches?

For some of the aligned photo, there are only a few lines presented, but there are many obvious features like corners, patterns. How come there are so few match lines?

Which measure does Photoscan use to judge whether the matches are correct?


Rosy

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Re: Questions about View matches in PhotoScan
« Reply #1 on: February 02, 2018, 04:11:39 PM »
Hello, can anyone help to explain? Many thanks!

Alexey Pasumansky

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Re: Questions about View matches in PhotoScan
« Reply #2 on: February 02, 2018, 05:57:37 PM »
Hello Rosy,

Blue lines are connecting valid (used) matching points between the selected pair of images, and red lines are connecting invalid (unused) matching points.

The reason of the very few number of matching points detected could be related to the processing settings used or to the quality of the images (high noise, image blur and etc.)
Best regards,
Alexey Pasumansky,
Agisoft LLC

Rosy

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Re: Questions about View matches in PhotoScan
« Reply #3 on: February 02, 2018, 06:08:39 PM »
Hi Alexey,

Thank you for the reply.

I'm a bit confused how come that such a few matching lines are presented in the aligned photos. Shouldn't there be a link between the number of valid matching lines (blue) and the alignment? Let's say, if photos are aligned, there should be at least how many blue matching lines...

Regards,
Rosy

Alexey Pasumansky

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Re: Questions about View matches in PhotoScan
« Reply #4 on: February 02, 2018, 06:16:45 PM »
Hello Rosy,

View Matches dialog represent the matching points only for the selected pair of images. You can sort the list of cameras by the number of matching points and if there are pairs that has considerably bigger number of valid matches.

In principle two images in the aligned set could have no matching points at all, if they are not overlapping, but they are still aligned, due to connection to other overlapping photos.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Rosy

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Re: Questions about View matches in PhotoScan
« Reply #5 on: February 02, 2018, 06:20:37 PM »
I see. Thank you very much

Felix_

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Re: Questions about View matches in PhotoScan
« Reply #6 on: February 05, 2019, 03:07:54 PM »
Allow me to dig up this thread again to get some further clarification of the question by Rosy:

Which measure does Photoscan use to judge whether the matches are correct?

I use Photoscan to calculate accurate camera positions using a calibration target with a nice pattern and known geometry. During the photo alignment Photoscan finds around 20,000 matches between image pairs, but marks all of them as invalid. This made me wonder about two questions:

1)  Based on which criteria does Photoscan decide whether a match is valid or invalid? (original question from this thread)

2) What would be the characteristics of an ideal surface pattern, that would lead to a maximum number of valid matches?

Cheers,
Felix
« Last Edit: February 05, 2019, 05:55:09 PM by Felix Grigat »