CloudCompare forum

Hi, thank sin advance for any information here.

https://drive.google.com/file/d/1sARStR ... sp=sharing

What is causing the file to become unusable after running the ALIGN tool?

Also, why is there such a large degree of error inherent in the aligned points?

Thank you much

I've found that the point cloud, gathered by Hovermap, needs to be scaled up by 3.7 times in order to be at the correct size.

Is this a cause for the situation?

Thank You

Hi,

If the scaling issue was consistent over the whole cloud (and in any direction - typically because of a unit issue for instance) then it wouldn't cause that much errors. Either the cloud is distorted (or the GCPs), or there's a lot of noise in the Z direction (it's not easy to see when only looking at the cloud from the top).

Then, the other issue is because the points are transformed in a global coordinate system with large coordinates. This causes a loss of accuracy because these large coordinates are not properly handled by CloudCompare or by OpenGL (so the issue is not only visual, it's also with the transformed points). Normally, CC should have asked you to "recenter" the points at some point in time (with a 'Global Shift & Scale' dialog). Of course that can cause some additional error, but once again, not that much compared to the 1st problem).

Can you maybe share the data with me? (admin [at] cloudcompare.org)

Daniel, thank you much for the response. I will send files now.

The reason I did not allow the points to be re-centered is because when I do that, Civil3D will not allow me to make a surface. If I don't allow the coordinates to be translated, the surface will come in.

I am certainly willing to allow it to translate as it needs to perform the tasks, but need the eventual output to match the GCPs collected in the field.

Also, it seems that in order to import GCPs into CC, I have to switch the X and Y axes. Obviously that then means I also need to find a way to transform the output from CC to be in NEZ (XYZ) format rather than ENZ (YXZ) for importation into Civil3D, where the mapping functions occur.

Thank You

Normally, you should be able to 'safely' center the points in CloudCompare, as it should be properly re-centered at export time. But it depends on the output format (most of them support large coordinates, apart from STL and a few others).