Classify points above and within a 3D polygon plane

[Bobby Riley]

Jochen,

Please review the attached DOC file and let me know your thoughts please.

Thank you,

Bobby

[Jochen Rapidlasso]

Hi Bobby,

please always submit your inquiries in a publicly readable format. We are now offering this service as a special Saturday morning service:

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I have a task where I need to reclassify road (and some other) points within thousands of bridge polygons across ~100k tiles to a new classification. The bridge polygon is 2D. I have draped the bridge deck polygon to the adjacent surface like seen below.

Reading https://groups.google.com/g/lastools/c/douHVoQLY7g/m/P99IWG9WAgAJ%20I%20believe%20las3dpoly64 I believe las3dpoly64 can perform the task given my envisioned constraints.

I want to reclassify all the points within the polygon, but I want to be somewhat surgical about it. Lasclip is too imprecise for what I want to do. I want to reclassify all the desired points above the plane the draped bridge polygon describes. I have tested las3dpoly64 but I am not seeing the results I want. Below is the syntax used.

C:\LAStools\bin\las3dpoly64 -v -i ..\.\2_PROCESSED_LAS\ROAD_CLASSED\*_R.laz -poly ..\.\1_SOURCE_POLYS\PROCESSED_BRIDGE.shp -distance 0.01 0.1 -match_all_above -ignore_class 0 2 3 4 5 6 7 8 9 10 18 20 -cores 20 -classify 13 -odir ..\.\2_PROCESSED_LAS\BRIDGE_CLASSED -olaz -odix _B

I was expecting (hoping) the -match_all_above flag would override the -distance 0.01 0.1 flag and classify all the desired points above the 3D plane, but that is not happening. Only points within the distance specified were classified.

Using -distance 25 1000 to see what effect it has points outside the polygon are changed, see below. This is unwanted.

So, I am curious to know if one can reclassify only the desired classes/points above the 3D plane, and not modify any points outside the 3D plane.

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We will have a look at this,

Cheers,

Jochen @rapidlasso

[Jochen Rapidlasso]

Hi Bobby,

las3dpoly is only intended for working along the edges of a polygon or polyline. To work/classify within a polygon area, lasclip is currently the only option available. You mention that it is a 2D polygon. In that case, however, it cannot have any height. Or do you mean 2D with a constant Z value?
lasclip offers the option to filter for a constant Z height using additional filters. This filtering can then also be combined with the actual clip operation.
I currently see this as the only option.
If this doesn’t work, we would have to consider either extending las3dpoly to include closed areas or extending lasclip to include a Z argument.
This would be possible in principle, but it would certainly take some time.

Cheers,

Jochen  @rapidlasso

[Bobby Riley]

Thank you for the feedback, Jochen.

Bobby