These are chat archives for PDAL/PDAL

16th
Nov 2017
matt wilkie
@maphew
Nov 16 2017 00:04
Wanted: ability to wildcard glob inputs and just specify an output folder and a process map, pdal pipeline --in=./data/*.laz --outdir=../results --json=process-pipeline.json, (output would be ../results/*.laz). Does this exist and I'm just not finding it?
pandu-rao
@pandu-rao
Nov 16 2017 17:31
i have a question about merging las files. let's say i have a pointcloud p, i extract some points px. the class of the px points are modified (pxm). i'd like to create a new pointcloud P by combining p and pxm. i can do this with pdal merge pipeline. however, the number of points in P are the sum of points in p and pxm. i want P to have the same number of points as p. any suggestions on how i might accomplish such merging?
Howard Butler
@hobu
Nov 16 2017 18:43
@pandu-rao you probably need a filters.range to filter out what you don't want to come through the merge. https://www.pdal.io/stages/filters.range.html
chambbj
@chambbj
Nov 16 2017 18:53
@maphew Sorry, my Gitter notifications seem to be off/broken. I never see these conversations until they are quite old! The mismatched [) is fine for any DimRange. Square brackets are used to indicate that the specified bound is inclusive. Parens indicate exclusive. So [2:) would be used to pass/assign every value >= 2.
As for PMF vs SMRF, I tend to prefer SMRF nowadays. PMF can still be useful. I’ve wrestled with whether or not to expose both through pdal ground given it’s convenience. SMRF is very good at stripping vegetation and can handle some terrain. PMF may be a bit better with buildings and flatter terrain. It’s all kind of a black art. I wish there were a silver bullet, but in my experience you have to play around with the parameters no matter which approach you use, open source like these or proprietary. We’ve done our besst to give you reasonable defaults for both PMF and SMRF (actually, they are usually straight from the published works).
Andrew Bell
@abellgithub
Nov 16 2017 20:19
@maphew: We encourage people to do directory looping with some sort of script mechanism. An example can be found at the bottom of this page: https://www.pdal.io/tutorial/reading.html. This keeps PDAL from getting too complex and provides you more control over file naming.
pandu-rao
@pandu-rao
Nov 16 2017 21:31
thanks! @hobu
Andrew Bell
@abellgithub
Nov 16 2017 21:32
@pandu-rao : Are you just trying to modify the the classification of some points? Perhaps what you want is filters.assign? https://www.pdal.io/stages/filters.assign.html
pandu-rao
@pandu-rao
Nov 16 2017 21:49
@abellgithub no, i need to take specific points out, do some processing and reassemble the parts
i'm already using filters.assign
matt wilkie
@maphew
Nov 16 2017 22:44
@chambbj thanks! Re: ground algo's. Jeffery S. Evans has opined in that (all?) Morphological Filters are problematic for non-urban terrain. How much work to add Multiscale Curvature Classification (MCC) ...or similar? (that being his preference).
@abellgithub re: looping - well in my case offloading the looping to users means more problems, 'cause I'm not very good at it! However I understand needing/wanting to concentrate your developer time in places providing the best return for you.