Thank you, StevenRamsey!
I still have a few questions then…
Why do you say the PTX files have no RGB? I used dummy RGB data, with 0 0 0 for invalid points and 255 50 50 for valid points. Is this not ok?
My original col x row is 512x424, but data you posted shows 510x524. Is this a typo?
Did you align the clouds using a third party software then update the .ptx files with the new translation & rotation matrix?
Or did you use RC for the entire process?
Could you give me some details about the steps to achieve this?