Start with .las or .ply in CC is better?

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ray1234
Posts: 5
Joined: Fri Oct 09, 2020 4:12 am

Start with .las or .ply in CC is better?

Post by ray1234 »

I obtained some raw data using handheld laser scanner.

After that, I can use GeoSlam Hub v5 to export the data to .las (without normal) or .ply (with normal) format to put in CC to remove the unwanted points to obtain a "clean" profile of some slopes.

Then my colleagues will use the "clean" data to form a 3D profile surface in Civil3D.
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My boss ask me to determine which data format .las / .ply I should use in CC to keep most amount of information.
When I input a .ply file, there are 11 fields data listed in CC belows (x,y,z Nx,Ny,Nz, RGB , intensity, point source ID)
Image

when I input a .las file, there are 13 fields I can tick (classification, time, point source ID, number of returns, return number, scan direction flag, edge of flight line, scan angle rank, user data, intensity, RGB)
Image

However, if I use .las file, I cannot find some buttons / settings related to the classification, number of returns, return number, scan direction flag, edge of flight line, scan angle rank, user data. Will these data be lost after doing some merge works in CC and then export to .las again?

People say "if you need to use software PlaneDetect, you must use .ply to do works in CC. "
Apart from this, is there any advantage using .ply than .las or vice-versa?

After doing some searching via internet, I didn't find any post saying it .las or .ply is better and which is better to input in CC to work to preserve most amount / most important data.

Can you give me some advices or ideas?
daniel
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Re: Start with .las or .ply in CC is better?

Post by daniel »

Ply is super extensible, and you can virtually save anything... but the big problem is that there's no real common agreement on how to use it. Therefore, not all software will manage properly PLY files generated by another tool.

And LAS is more rigid (there's a given number of 'official' fields, and you don't have the choice for their name, etc. But recent versions of LAS supported extended (= custom) fields as well which lets you save any scalar field to a LAS file.

Mind that theoretically LAS files contains all the default fields you listed below (classification, number of returns, etc.) but they might not be used. By default, CC will discard them if they are empty or if all the points have the same value (however there's a checkbox to force CC to load the fields nevertheless).
Daniel, CloudCompare admin
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