CloudCompare forum

Hello,

I want to compare two point clouds in Cloud Compare. I've scanned two point clouds of the same surface. The surface is a rock in a mountain side. I want to check if the rock has moved, if there is a difference between the first scan and the second scan. We have tried to compare the clouds with different tool, cloud to cloud, and mesh to mesh and get different standard deviations. The standard deviation are also higher than expected (4 cm). We placed the scanner at the exactly the same position, the same day so there should be no movement. Which way is the best way to do this comparison?

- Michelle

What does the distance distribution look like? And how are they distributed over the cloud?

The high values can come from the density variations and missing data (when performing C2C) or from the way the mesh has been created (when performing C2M) and last but not least from the scanner noise / inaccuracies.

If you can mesh the reference cloud properly then it will avoid the first issue. But to avoid the two first issues you should try to use the M3C2 plugin (but you'll have to understand most of the parameters). And of course the last issue is a little bit more problematic

Don't hesitate to send me the clouds if you can. I'll quickly tell you where the distances come from.