CloudCompare forum

Hi,

I'm new to the software and am slowly learning its functionality. I have been comparing two point clouds first by a manual alignment and then using ICP.
My question is when I perform a manual alignment why does it produce a bimodal histogram, yet a smaller RMS than when the ICP is performed?

Any help would be greatly appreciated.

Well, in the general case I would say that the RMS is just the mean of the square errors (well the square root of it). So as all averaging process, it can 'hide' a lot of things.

In your particular case, are you referring to the RMS output by the registration tool? Because in the case of the alignment tool, the RMS is only computed on the points that you have picked. Not on all the points of the cloud. While with ICP, it is computed with thousands of points (by default CC will take up to 50000 points randomly at each iteration).