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"Interlaced" Point Cloud

Posted: Wed Jan 24, 2024 4:07 am
by Dronkey1679
I don't know the exact wordings to describe the issue I am facing. Basically I am trying to use CC to regenerate some surfaces with removed vegetations and structures from a point cloud generated with drone images using WebODM and similar software so I can get some cleaner surfaces to measured the volume and contour since I do not have a LIDAR drone. And I have not been able to view the point cloud in CC correctly due to the "interlaced" visualization shown below (please right click to open in a new tab for a large view...):
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This is the sampled area zoomed out
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Zoomed in...

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And the point cloud viewed in WebODM or Pix4D (with some trees and vehicles removed)

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Zoomed in...

It is unlikely a point cloud density problem I guess but I have tried loading a sample point cloud I downloaded from the internet and there was not such interlaced problem.

Any help would be highly highly appreciated!

Re: "Interlaced" Point Cloud

Posted: Thu Jan 25, 2024 9:32 pm
by daniel
This very much look like the very classical problems of large coordinates... Did you see a warning about large coordinates and a suggestion by CloudCompare to apply a 'Global Shift'? Did you accept it? Or was maybe the default shift suggested not large enough to (temporarily) reduce the coordinates to small enough values?

Otherwise you'll get this issue due to the loss of numerical accuracy.

Re: "Interlaced" Point Cloud

Posted: Fri Jan 26, 2024 8:10 am
by Dronkey1679
Hi Daniel,

Oh yes, it's definitely a co-ordinate problem and I never thought of that. I declined the Global Shift every time because I thought it was better to keep the local CRS as I needed to segment the point cloud with a georeferenced polygon! Turned out it's my misunderstanding of how the software works. Really appreciate the help and clarification!