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Author Topic: What causes these random bubbles/disks in point cloud?  (Read 3351 times)

aggieair

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What causes these random bubbles/disks in point cloud?
« on: January 15, 2016, 01:38:10 AM »
Sometimes I get these circular bubbles/disks in my point cloud.  Almost looks like frozen bubbles in a lake.  I generally leave them be as the rest of the image is pretty good.

Any idea what causes this issue?  This area has overlap from two flightlines (the two flightlines make almost an X in this area).  However I've seen it on straight flghtlines that appear to have decent overlap.

Do you get this issue?  If so, how to you fix it?

bigben

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Re: What causes these random bubbles/disks in point cloud?
« Reply #1 on: January 15, 2016, 05:25:57 AM »
Waves move.  For each flight path the waves between consecutive frames are similar enough to align/mesh, but between flight paths they are too different... so you're getting part of your mesh from one flight path, and part from the other.  But because the waves have moved between shots the distance won't be accurate and you can get different hieghts for each flight path.  If correct, this could be confirmed by selecting points in each section and filtering the cameras.

frank.stremke

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Re: What causes these random bubbles/disks in point cloud?
« Reply #2 on: January 15, 2016, 02:36:10 PM »
i ahd similar problems a while ago these are alignment problems i have when combining diferent flights and also it hapens towards the edges of a model when the overlap is not great
i could not find a way to fix it without redoing some of the fotos...
frank

Alexey Pasumansky

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Re: What causes these random bubbles/disks in point cloud?
« Reply #3 on: January 15, 2016, 02:47:48 PM »
Hello aggieair,

Such artifacts  are usually related to the misaligned cameras in the given area. For example, when the images from the overlapping flight lines do not have any matching points but cover the same area. So usually it is a result of alignment problems.
Best regards,
Alexey Pasumansky,
Agisoft LLC

aggieair

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Re: What causes these random bubbles/disks in point cloud?
« Reply #4 on: January 16, 2016, 01:00:20 AM »

Hello aggieair,

Such artifacts  are usually related to the misaligned cameras in the given area. For example, when the images from the overlapping flight lines do not have any matching points but cover the same area. So usually it is a result of alignment problems.

Would trying out various Align values help this?  Or given the set of imagery (assuming you can't refly) there is no way to improve things?

Alexey Pasumansky

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Re: What causes these random bubbles/disks in point cloud?
« Reply #5 on: January 16, 2016, 01:02:59 AM »
Hello aggieair,

You can try fixing it trying different settings. In case the subsets of images are really not aligned with each other, you can try using disabled preselection for this particular area to see whether the images can be matched at all.
Best regards,
Alexey Pasumansky,
Agisoft LLC