Alignment of two point cloud

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mehmetvozdogan
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Alignment of two point cloud

Post by mehmetvozdogan »

Hi,

I have two registered point cloud data of same place. They are taken in various dates.
But both of the point cloud have own coordinate system.
I need to align (not register) the both point clouds for m3c2 analysis.
I can manually align it but precision of alignment depends on user.

Is there any other methods for alignment of two point cloud data for more precision leveling.

Thank you...
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danielgm
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Re: Alignment of two point cloud

Post by danielgm »

Once both clouds are roughly aligned you can use the 'ICP' tool (https://en.wikipedia.org/wiki/Iterative_closest_point). This should reduce user-dependent errors (but it's still necessary that both clouds are already roughly aligned before using this tool).

Mind the 'overlap' parameter that is the only one that you should really care about ;)
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mehmetvozdogan
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Re: Alignment of two point cloud

Post by mehmetvozdogan »

danielgm wrote: Tue Feb 19, 2019 8:46 pm Once both clouds are roughly aligned you can use the 'ICP' tool (https://en.wikipedia.org/wiki/Iterative_closest_point). This should reduce user-dependent errors (but it's still necessary that both clouds are already roughly aligned before using this tool).

Mind the 'overlap' parameter that is the only one that you should really care about ;)
Hi Danie,

Thank you for your answer but i think if i use ICP tool, shape of one point cloud will change according to references poin cloud shape.

i have two various dated point cloud data of underground drift and i want to determine the deformation of drift. So shape of the point clouds must be prevented. The alignment must be done with only rotation of point cloud
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Re: Alignment of two point cloud

Post by danielgm »

ICP doesn't change the shape (if you don't check the "Adjust scale" option). It will only move the aligned cloud.

Both the ICP and the 'Point pair based' alignment tools produce (and apply) a rigid transformation matrix on output.
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mehmetvozdogan
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Re: Alignment of two point cloud

Post by mehmetvozdogan »

danielgm wrote: Tue Feb 19, 2019 9:41 pm ICP doesn't change the shape (if you don't check the "Adjust scale" option). It will only move the aligned cloud.

Both the ICP and the 'Point pair based' alignment tools produce (and apply) a rigid transformation matrix on output.
Thank you for the help and information Daniel..
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Daniel Wujanz
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Re: Alignment of two point cloud

Post by Daniel Wujanz »

Dear Mehmet,

it is vital that you remove the areas that are subject to deformation BEFORE you apply the ICP! Otherwise the transformation parameters will be biased and your deformation map will be rubbish. If you're interested why this happens please have a look at the following article (if you don't have access I can also send you a pdf): Wujanz, D., Krueger, D., & Neitzel, F. (2016). Identification of stable areas in unreferenced laser scans for deformation measurement. The Photogrammetric Record, 31(155), 261-280.

All the best

Daniel
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