"Blanket effect" - remove/filter points on ground

[kjetilbmoe]

Hello,
I'm happy to have found this software, it looks very promising. I'm doing a wind analysis and have lots of laser measurements available, so I'm aiming to export in the end as .stl. What I need is a surface with mostly the terrain and slope, but houses and vegetation could as well show up as "bumps". The problem is that the measurements have reached through tall trees, and so that ground points exists just below trees, and so the mesh becomes very bad in these regions. The scalar fields does not allow me to isolate these regions properly. How can I best filter out what's "below" the trees? See attached screenshot.

I need to find an automatic way to do this, as the area is very big, and cannot be done manually.

I tried to smooth the points, but that didn't propely smooth for the tress, as there is a significant vertical distance. Do you know of other ways?

At best, there would be a SOR-like function that works only in the x-y plane, and could remove those points "on the ground". Would this be possible?

[daniel]

You should definitely take a look at the qCSF plugin: http://www.cloudcompare.org/doc/wiki/in ... F_(plugin)

There are other ways to achieve similar results (you can find interesting posts on the forum about this topic), but this plugin is particularly efficient!

[kjetilbmoe]

Thank you for your quick reply! Had a look at the CSF plugin, it might do the work, but I haven't quite found the right input parameters yet. Also, it seems this qCSF plugin puts the cloth on from bottom-up? I'm looking for a top-down cloth dropping. (Perhaps I should transform/flip the cloud first?)

I did another try by removing points classified as vegetation, and I see that edges on particularly houses gets very rough. Should this be smoothed before or after making the mesh? I have had a brief look on the MLS.

[kjetilbmoe]

Can I modify the CSF plugin to cancel the terrain inverse operation? I believe this is all that is needed to produce the mesh.

[daniel]

Sorry, I read your email to fast, and I thought you only wanted the ground... Not sure that CSF will help you if you want to keep the buildings.

Then maybe you could try to 'classify' and remove the vegetation. In this case, you should take a look at the Canupo plugin.

Otherwise, not sure how you can easily revert the CSF plugin operation, but you can multiply the cloud along Z by -1? (with Edit > Scale / multiply)

[kjetilbmoe]

Thanks. The vegetation is already classified. But - seen from above - the tree canopy is mixed with ground points in between as well. This makes a very rough mesh surface as there might be many meters "z" distance between very closely located points in xy plane.

On the other hand, if I was able to project regions of classified vegetation in z direction, maybe I could subtract these ground points which are directly below the vegetation points, using the same regions?

[daniel]

Well maybe... but I don't really know how to do this with CC ;)