[pdal] Extract terrain from TLS point cloud

[Luigi Pirelli]

we had similar problems with TLS in urban context regarding first part pf
the cars
you can see our strategy to clean the first PMF effect in slides from
http://slides.com/darango/deck-10-11-12-11-12#/11
to
http://slides.com/darango/deck-10-11-12-11-12#/1
<http://slides.com/darango/deck-10-11-12-11-12#/11>5

the main idea is to do noise cleaning, PMF, filter on normal, filter on
kdistance, PMF again

not clear to me if you can have a good discrimination of the ground part of
the threes using normals due to nature of these surfaces.

cheers

Luigi Pirelli

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On Sat, 11 May 2019 at 10:01, Silvia Franceschi <silvia.franceschi at gmail.com>
wrote:

> Dear all,
> I am trying to extract the ground points from a point cloud of a
> terrestrial laser scanner (TLS) in a forestry environment, but the result
> is not so good as the one I got using data from ALS.
> What I did is:
> 1. denoise the dataset using the filter.outlier and a filter.range for Z
> ranges:
>             "type": "filters.outlier",
>             "method": "statistical",
>             "multiplier": 3,
>             "mean_k": 8
> 2. apply a filter.elm and a filter.smrf to the cleaned dataset
> For the SMRF filter I used these parameters:
>             "type": "filters.smrf",
>             "slope":0.2,
>             "window":16,
>             "threshold":0.45,
>             "scalar":1.2
>
> Unfortunately the resulting ground points contain also the first part of
> of the trunks of the trees, how is it possible?
>
> I am doing some testing changing the values of the SMRF parameters but the
> results are almost the same.
>
> Do some of you have experience with such kind of data? Am I missing some
> operation for filtering? Could you please help me understanding at least
> where to focus the attention to try to obtain something...
>
> Thank you in advance.
>
> Silvia
>
>
> --
> ing. Silvia Franceschi
> Via Roma, 64
> 38030 Castello di Fiemme (TN)
>
> tel: 0039 -3384501332
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