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Author Topic: Adding images to existing aligned image set?  (Read 5118 times)

andyroo

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Adding images to existing aligned image set?
« on: December 05, 2014, 03:37:57 AM »
Is there any way to add images to an existing aligned image set (with or without GCPs)?

So far the only way I found was to realign all images after adding the new ones. It would be great to be able to keep the existing aligned images and align the new images to them.

My reason - I am flying with two cameras. One of them is highly overlapping but I have focus problems (Ricoh GR focused to infinity but not behaving, possibly because it's mounted slightly upside-down) The other (Canon D10) has crisp imagery, but is less overlapping (3 second interval instead of 2, narrower FOV). Also the Ricoh is a prime lens and builds a nice terrain with no smiles or frowns. The Canon is not and is more dependent on GCPs.

I want to first align the Ricoh GR images, add GCPs, and optimize, then add the Canon D10 images without re-aligning the GR images. But I think I have to re-align everything once I have the GR aligned and optimized.

Any tips are appreciated.

Alexey Pasumansky

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Re: Adding images to existing aligned image set?
« Reply #1 on: December 05, 2014, 01:02:16 PM »
Hello Andy,

PhotoScan doesn't store feature points found on the Detect Points step, so it is impossible to match two separate aligned sets.

Best regards,
Alexey Pasumansky,
Agisoft LLC

andyroo

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Re: Adding images to existing aligned image set?
« Reply #2 on: December 25, 2014, 09:22:21 PM »
Thank you Alexey,

I wonder if you might have any advice about this outcome - When I align one camera (Ricoh GR) I get a more extensive coverage than when I align both cameras together, or when I align only the other camera (D10). Can you think of a way for me to re-align that might better reconstruct both? Is there a way to prioritize which cameras try to align first?

ThomasVD

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Re: Adding images to existing aligned image set?
« Reply #3 on: December 20, 2018, 10:25:20 AM »
A similar issue (and possible solution):
I want to add images to an existing alignment, I don't mind having to re-align all images, but the images that are already aligned should stay in approximately the same position.

Concretely the situation is:
- I've just processed a dataset of ca 15 000 video frames of an underwater shipwreck site. Because of bad visibility, bad lighting and bad overlap there has been a lot of manual work involved in getting all the images to align (a lot of "reset camera alignment, align selected cameras, manual marker placement and optimisation"), so I've worked on it for various days in order to get this far.
- Now I've received 400 additional, good images of the site from my client. The new photos probably won't contribute much to the geometry but could be very good for texturing.

=> I want to align these 400 images to the remaining 15 000 video frames without changing the position of the original images (too much).

Would this be the correct workflow?

- In the PhotoScan document with 15 000 aligned video frames, save the camera calibration of each camera group from the Camera Calibration menu.
- In the PhotoScan document with 15 000 aligned video frames, go to Reference pane, click "export", choose ".txt" format (PhotoScan says: "can't export reference data when I choose .xml)
- export the "cameras" making sure "save location" and "save rotation" are checked. In my case the estimated values will be saved, since I don't have ground control coordinates.

- make a new PhotoScan document, import the 15 000 image frames previously aligned.
- in the Camera Calibration menu, import the previous camera calibration of each group and check "fix calibration"
- in the reference pane, click "import", choose the .txt file containing my old reference data, and set XYZ and Yaw, Pitch, Roll column to match the column containing the estimated values from my previous alignment. If I now switch on cameras in 3D view, a blue ball appears for each camera location (shouldn't this be a blue square with a line, to show that the camera rotation is also known?)
- under Reference Settings adjust Camera Accuracy to something small like 0.05m => ie the cameras can only move 5cm from their current location? (how does this work when the alignment is not scaled yet?)
- add the 400 new images to the same PhotoScan document
- align all 15 400 images together. My settings would be: medium accuracy, generic preselection on, reference preselection on (so it uses the previous alignment), key point limit 40 000, tie point limit 0, adaptive camera model fitting checked (unless someone has suggestion as to why another setting would be better).

Hopefully by importing the Reference data and setting a strict camera accuracy PhotoScan will keep the old positions (more or less) and have an easier time aligning the images relative to each other (when compared to the very manual first time alignment)? I would appreciate any input from the community and developers!

Cheers,

Thomas

Kiesel

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Re: Adding images to existing aligned image set?
« Reply #4 on: December 20, 2018, 12:37:44 PM »
Thomas,

I have thought, that this is already been solved in newer versions (you have reopened a very old thread from 2014). In Preferences/Advanced you can check "Keep key points" and in "Align Photos" you can uncheck "Reset current alignment".

Best regards

Alexey Pasumansky

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Re: Adding images to existing aligned image set?
« Reply #5 on: December 20, 2018, 03:27:43 PM »
Yes, incremental alignment has been added in the version 1.4.

Just make sure that Keep Key Points option has been enabled prior to the image matching operation. After that when new images are added to already completed alignment don't check on "Reset Current Alignment" option in the Align Photos dialog to ensure that the newly added images will be matched to previously detected key points.
Best regards,
Alexey Pasumansky,
Agisoft LLC

ThomasVD

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Re: Adding images to existing aligned image set?
« Reply #6 on: December 21, 2018, 02:14:05 AM »
Oh wow, I somehow totally missed the fact that this feature had been added, thank you Kiesel and Alexey for responding so quickly and pointing it out - really glad to hear it's been introduced!

I had searched the forums for "add image to existing alignment" (and similar search queries) but couldn't find much, which is why I revived this thread from 2014, but of course now that I search for "incremental alignment" I get a lot of info on the new workflow.

However since I didn't know the feature existed I didn't have "Keep key points" checked in the Preferences pane :( Would the workflow as I described it above still work as a work-around for this particular case?

Kiesel

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Re: Adding images to existing aligned image set?
« Reply #7 on: December 21, 2018, 01:29:15 PM »
Hello ThomasVD,

because you don't have key points for aligned 15 000 key frames anymore, which are needed to generate tie points betweeen old and new photos, I doubt that you can align the new photos with them without generating new key points for all 15000 photos again.

The only other way I see, is to generate a new chunk for new photos, align all 400 photos in new chunk (if that is possible?), then set identical named markers in both chunks (15000 and 400; markers are your tie points) and then align both chunks by markers.

Regards

Eric Baird

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Re: Adding images to existing aligned image set?
« Reply #8 on: January 03, 2022, 03:26:59 PM »
I think this is an important feature, but one that a lot of users might not realise is available.

I'd experimented with adding a block of photos to a chunk and using the "align photos" option, but since it did nothing, I just assumed that it didn't work. If I'd known that all one has to do is change that setting first, I'd have been using it a lot.

I think there's an issue here with "ease of discovery" -- If one tries to align a block of photos with the setting "off", then instead of failing silently, perhaps the program could throw up an alert box letting the user know that the setting needs to be on for this feature to work.