[pdal] filtering duplicate points

[Andrew Cunliffe]

Thanks for the suggestion Mike,

I just tried running
                        {
                            "type": "filters.sample",
                            "radius": 0.001
                        },
on a test cloud with n = 6650 points. With a 0.001 m threshold CloudCompare
removes 1782 as duplicates (ca. 27%), and makes no visible difference to
the displayed cloud, so the points removed appear genuine. However, with
the above parameters, this PDAL pipeline only removes 6 duplicates.

I wondered whether filters.sample perhaps only considers proximity in XY
space? (this isn't currently specified in the documentation
<https://pdal.io/stages/filters.sample.html>). Apologies if I have missed
something simple, I'm still learning PDAL, but I like it.

Thanks,
Andy



On Mon, 13 May 2019 at 13:26, Michael Smith <michael.smith.erdc at gmail.com>
wrote:

> Andrew,
>
>
>
> You can use filters.sample and just set a small radius.
>
>
>
> Mike
>
>
>
>
>
> --
>
> Michael Smith
>
> Remote Sensing/GIS Center
>
> US Army Corps of Engineers
>
>
>
>
>
> *From: *pdal <pdal-bounces at lists.osgeo.org> on behalf of Andrew Cunliffe <
> andrewmcunliffe at gmail.com>
> *Date: *Monday, May 13, 2019 at 8:21 AM
> *To: *PDAL Mailing List <pdal at lists.osgeo.org>
> *Subject: *[pdal] filtering duplicate points
>
>
>
> Dear all,
>
>
>
> I am hoping someone might be able to help me to use PDAL to filter for
> duplicate points in a point cloud.
>
>
>
> By duplicate, I mean points that are less than a threshold distance (e.g.
> 0.001 m) from other points in the cloud. I'm working with
> photogrammetrically-generated point clouds, in some cases ca. 20-30% of the
> points are 'duplicates' so removing these has some big benefits later in
> the pipeline.
>
>
>
> I'm looking for a filter that functions like 'Remove duplicate points
> <https://www.cloudcompare.org/doc/wiki/index.php?title=Remove_duplicate_points>'
> in CloudCompare. I wasn't able to see anything suitable under the filters >
> cull documentation, unless filters.voxelcenternearestneighbor would
> achieve this with cell set to 0.001?
>
>
>
> If anyone else thinks that a filter.duplicate function might be helpful,
> I'm happy to submit a feature request via Github.
>
>
>
> Thanks
>
> Andy
>
>
> --
>
> Dr Andrew Cunliffe
>
> Research Fellow
> School of Geography
> University of Exeter
>
>
>
> _______________________________________________ pdal mailing list
> pdal at lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/pdal
>


-- 
Dr Andrew Cunliffe

Research Fellow in Dryland Carbon Dynamics
School of Geography, College of Life and Environmental Science,
University of Exeter

UoEx Profile
<http://geography.exeter.ac.uk/staff/index.php?web_id=Andy_cunliffe>
Google Scholar
<https://scholar.google.co.uk/citations?user=GEfm3PIAAAAJ&hl=en>
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