CloudCompare forum

I'm still a new user, and generally self taught in photogrammetry/geo imaging (still learning). I have been trying to monitor small changes in plasters using photogrammetry as part of my MA dissertation in wall painting conservation. When I push my clouds to compare very low levels of change, my results show a grid pattern (See images). Does anyone know where this grid pattern comes from? I'm thinking it's some form of interference, but I can't quite understand it.
Any ideas would be appreciated!

It can come from the generation method (scanner / photogrammetry algorithm) but it can also come from the reference cloud density if the distances are very low. Check the C2C wiki page. To remove any such effect, use a local model, or even better use the more evolved M3C2 plugin.

A last culprit could be the numerical accuracy if you used too big coordinates (in which case it's a better idea to accept the Global Shift suggested by CC).

Thanks very much!