Wall or Surface Deformation Study Cloud to Cloud Analysis

Deformation Analysis Software for 3D Point Cloud Data eg CloudCompare
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D2RSURVEY
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Wall or Surface Deformation Study Cloud to Cloud Analysis

Post by D2RSURVEY »

Hello

After preforming a verticality check on a hospital facade, checking for potential wall tie failure or lack there of, the client later asked if I could return in 6 months and check for deformation. I said yes, although I have never carried out a cloud to cloud analysis before. So I had removed all my original targets, and I didn't fancy setting out my original scan positions or installing new targets, as the building is vast.

I figured if I scanned near to the original positions (I don't need as many scans this time) and registered the new scans to at least two adjacent original scans, then isolate the new scans, I would create the 2nd visit point cloud. Logically, I masked out the subject building, so its data wasn't used in the registration in case any deformation skewed the registration.
Screenshot 2023-11-29 140410.png
My question is, do you think this was necessary? Or should the registration process be able to ignore any deformed areas and only use areas which are still corresponding. I am using SCANTRA plane to plane registration inside Z+F laser control. Some scenes have few objects other than the facade in question, so I have reduced registration confidence, and we have some anomalies in the results.
Screenshot 2023-12-04 123142.png
I was also thinking that I should have picked out the adjacent scans from the original set and not used the whole cloud? If I return in another 6 months, I was going to scan near to the 2nd set and register back to the original matching the connections.

I also thought I should have equally decimated each cloud before analysis?

Any advice much appreciated. This will be a really useful workflow as opposed to fixed prisms.
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Jamesrye
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Re: Wall or Surface Deformation Study Cloud to Cloud Analysis

Post by Jamesrye »

If you're just analysing how flat the wall is (relative to a vertical plane) then you don't care about coordinates, or tying back into the original survey.

If it's a proper movement monitoring project, then you need to have fixed monuments that you tie to each time. These need to be in an area that you are certain isn't moving. Also, you want to level between these fixed monuments and shoot them in with a total station each time so that you are sure they haven't moved and that your scan results are valid.

Tying the survey to the previous one using cloud alignment only is no good. How accurate is that? Can you prove it?

You don't need to decimate the work prior to analysis - unless you wanted to do a labelled grid at meter spacing or something. Not all clients 'get' the colored analysis map.
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