[pdal] tweaking parameters in filters.smrf

[Karl North]

Brad:

Thanks for the suggestions.

I’ve done some reading and begun playing around with the cluster filter.  One problem is that I’m new enough to PDAL that I cannot find a way to add/define a dimension and store the cluster ID into either LAS or LAZ format on output.  I think it should be possible to just hijack an existing field in the point data records for current testing purposes.  Does this sound possible?  I’m floundering a bit trying to find an example of something similar.  Can you point me in the right direction?

I can get a BPF output, but currently have no way to review the result.  I’m now downloading 64-bit QT Reader, after finding a thread by HoBu saying that this viewer would work for a quick review.

I’ve also tried using pdal translate to convert the BPF to LAS, but cannot find any trace of the ClusterID in the resulting LAS file.

Thanks for any and all assistance,

Karl


From: Bradley Chambers <brad.chambers at gmail.com>
Sent: Friday, June 7, 2019 11:29 AM
To: Karl North <karln at surdex.com>
Cc: pdal at lists.osgeo.org
Subject: Re: [pdal] tweaking parameters in filters.smrf

Karl,

On Fri, Jun 7, 2019 at 12:09 PM Karl North <karln at surdex.com<mailto:karln at surdex.com>> wrote:
The main issue that I currently have with my PDAL result is the presence of too much high frequency “noise” visible in the surface defined by the ground classified points.  A lesser issue is the delicate balance, when using the cut grid parameter to help eliminate building points, between the removal of building features and preserving sufficient terrain detail.

The issue you've mentioned with and without cut is well known. It would be interesting to hear more about what you are seeing with the high frequency noise though.

Is there anyone out there on the mailing list that can suggest such write-ups, or would be willing to share their insights?

I don't know of any write-ups other than the original paper. The original author also has his MATLAB code on GitHub (https://github.com/thomaspingel/neilpy<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fthomaspingel%2Fneilpy&data=02%7C01%7C%7C35f7a44a37464bc883b508d6eb65467b%7Cbf4323beeac04c8eb466c7924493cbee%7C0%7C1%7C636955217559063804&sdata=xQBCVsQE1yDqpbQ1PKAcVye54Atp8s3H2vY6854qdYU%3D&reserved=0>), though I don't recall that there are any hints on what parameters to tweak for specific environments.

Perhaps there are other (as yet undiscovered) PDAL filters that I might include in my pipeline either before or after SMRF that would be better suited to the remaining cleanup than tweaking the SMRF parameters themselves.

One thing that comes to mind, though it would take some experimentation, would be to run a cluster filter (https://pdal.io/stages/filters.cluster.html#filters-cluster<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpdal.io%2Fstages%2Ffilters.cluster.html%23filters-cluster&data=02%7C01%7C%7C35f7a44a37464bc883b508d6eb65467b%7Cbf4323beeac04c8eb466c7924493cbee%7C0%7C1%7C636955217559063804&sdata=Ot3hDXkA39602%2FrlxqvummbpIRBkd1xB9mPvl%2BuikdA%3D&reserved=0>) after SMRF and then to filter out clusters that were small. I'd maybe use this without cut to find those roof segments that got left behind and may end up as their own clusters.

I can share sample LAZ data illustrating a SMRF-vs-TSCAN comparison of current my state-of-the-art, if this will help clarify the current issue(s).  To do so, I could use some guidance on reasonable limits on file size for sharing such a sample.

It would certainly be interesting to see the data. Other users in the past have posted to Google Drive, Dropbox, or similar.

Brad
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