Aligning different scans of same object

[h.coll123]

Hi,

I have 2 point clouds (of the same shipwreck) taken at different dates with different laser scanning equipment and setups. I want to compare them, but the coordinate system is different in each (1,1,1 in the first pt cloud may be 6,4,-7 in the second etc.). I am new to cloudcompare and tried Tools-registration-align, but this requires picking equivalent points and I don't know these. There are a different number of points (10mil and 15mil) so I don't think there are equivalent points.

Is there a way of aligning these point clouds please? Maybe if I could centre each scan and get them scaled the same they would be on top of each other? Sorry for the stupid question, and if I have repeated the question of someone else.

May thanks,

Hugh

[daniel]

Follow the instructions here: https://www.cloudcompare.org/doc/wiki/i ... gistration

Especially point 2.2 (to achieve a first "rough" registration) and then 2.4 (to automatically and finely register the two clouds). Since they are potentially different, make sure to se the 'overlap' parameter of the ICP algorithm to something not too big (e.g. 70%).

(And for the 'Align' tool, the equivalent points should be manually selected at some key points on the structure)

[h.coll123]

Thanks Daniel, I have only just seen your reply but it is greatly appreciated!

[h.coll123]

Hi Daniel, I have aligned and am trying to apply the transformation matrix in matlab for confirmation.

Would (A' = A*T) be the correct way to transform A to the new pt cloud A' ?

[daniel]

Normally it should be the opposite (A'= T * A).