[pdal] Delete low points below surface

[Bradley Chambers]

I’d be interested to know what ELM parameters you used. It is configurable,
though perhaps still difficult to fine tune.

On Mon, Nov 10, 2025 at 06:38 Roland Spielhofer via pdal <
pdal at lists.osgeo.org> wrote:

> Hi,
> I am loking for a PDAL pipline to get rid of low lying points.
> The point cloud I am working with is very dense and represents the surface
> of a concrete pavement.
> The slabs of the pavement are divided by joints - and the points lying in
> these joints just below the surface I want to get rid of.
>
> I created some images showing details of one joint:
> https://imgur.com/a/oX7dZcE
>
> The surface is very flat, and the point density is ~ 5 mm in transversal
> and 20 mm in longitudinal direction (=driving direction).
> The joints have a depth of ~40 mm (see images).
>
> I tried out the elm filter, but I guess that the relative z-difference
> between the points is too little to mark them as noise.
>
> Any idea to filter the points in the joint with PDAL would be appreciated
> (I can also provide the LAZ pointcloud itself for experiments).
>
> Thanks in advance and best regards,
> Roland
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