How to extract buildings from a lidar (LAS) file?

[jcb]

Hello

I'm new on LIDAR and I'm trying to use CloudCompare (very good program and free ...).
I have extract building from OpenStreetMap for my City (Brindas 69126 France).
I have Lidar files of my town that I retrieved on the site of (Le Grand Lyon) format .las.
I can view the files with CloudCompare and I can do an extraction of the building with the scalar fields (classif value) and the SF Display params with only '6' ....
But if I click on register, I have all the informations .... I just want to register the buildings ... and nothing else ... for the moment ...

How can I do ?

Thanks for the very good job ...

[daniel]

Have you extracted the buildings as a new cloud? (with 'Edit > Scalar fields > Filter by value)

[jcb]

Hello
Thanks for the response.
It was exactly what I was looking for.

Now I try to recover the prints of the roofs to reproduce them in 3D.

[jcb]

Hello ...

In complement, I have anothers questions ... my objective is to build a city in 3D ... if I can and if It is possible ... of course ...

So I have a shape layer from which I extracted the nodes.
From these nodes, I would like to recover the altitudes from the lidar layer of the roofs I created at the moment.
How do I proceed using cloudcompare?

Thanks for the help .... and for this program again ..

[daniel]

Hum, I'm not sure to understand... You want to get the altitudes for 'nodes' (are they single 2D or 3D points?) from the lidar (roof) cloud?

You can't do it with the GUI version of CC at least. You could do it with the CC_CORE_LIB library (and qCC_db and qCC_io if you want to load the file) but you would need to develop some code of course...

[jcb]

Hello
Is it possible, from a lidar file, to obtain a file shape (shp) with its associated dbf file (identifier of the point and maximum altitude)?
I would like to compare this file (and its associated dbf) with the shape containing the contours of the buildings.
By associating, by localization, these two files I will be able to reconstitute the heights of the forming points the angles of my walls.
The goal is already to produce 3D flat roof buildings.

For instance, when I register a shape file I obtained a dbf with one information (local_idx 1).

Is it possible to have, for each point, an idx and the maximum height (for example) ?

Thanks for the reply.

[Chris]

Hey jcb,

Are you trying to constrain the point cloud to planar values created through your .shp file? I think I'm understanding that you would like to do two things:
-Remove the buildings from pointcloud A, creating a building layer (Point Cloud B). From point cloud B, you want to constrain the sides of buildings to planes that you create, so that they are "flat." This would be, I'm assuming, to create orthoplanes for texture generation...?

-You want to compare the contours of pointcloud A without buildings to the contours of point clouds A&B combined once B has undergone the process above.

Is that correct?