[pdal] FW: Attempting to filter out (1) Unclassified points flagged as Withheld
Andrew Bell
andrew.bell.ia at gmail.com
Wed Aug 4 07:14:49 PDT 2021
"where" is supported for writers as of version 2.3
On Wed, Aug 4, 2021 at 10:13 AM Bradley Chambers <brad.chambers at gmail.com>
wrote:
> Rose,
>
> As Andrew suggested, the withheld bit is actually stored in ClassFlags for
> your data. In this case, withheld returns are marked as "4" (see the LAS
> spec for more on the flags).
>
> $ pdal info CL2_BR20_2020_1000_4134.laz --filters.stats.count
> "Classification,ClassFlags" --filters.stats.dimensions
> "Classification,ClassFlags"
> {
> "file_size": 8728570,
> "filename": "CL2_BR20_2020_1000_4134.laz",
> "now": "2021-08-04T08:51:53-0500",
> "pdal_version": "2.2.0 (git-version: 3dd320)",
> "reader": "readers.las",
> "stats":
> {
> "statistic":
> [
> {
> "average": 2.3644045,
> "count": 2524409,
> "counts":
> [
> "1.000000/759595",
> "2.000000/1154344",
> "3.000000/160785",
> "4.000000/135106",
> "5.000000/9930",
> "6.000000/304542",
> "7.000000/106",
> "18.000000/1"
> ],
> "maximum": 18,
> "minimum": 1,
> "name": "Classification",
> "position": 0,
> "stddev": 1.55327344,
> "variance": 2.412658379
> },
> {
> "average": 1.159550612,
> "count": 2524409,
> "counts":
> [
> "0.000000/1792614",
> "4.000000/731795"
> ],
> "maximum": 4,
> "minimum": 0,
> "name": "ClassFlags",
> "position": 1,
> "stddev": 1.814840525,
> "variance": 3.29364613
> }
> ]
> }
> }
>
> Also, the where option is not supported on reader/writer stages, so you
> actually should've seen an error if you executed the pipeline that you
> shared. If you simply want a pipeline to extract non-withheld points, you
> can use the range filter. If you want to skip withheld points, but not
> discard them, you could use where with the other filters in your pipeline.
>
> Brad
>
> On Wed, Aug 4, 2021 at 8:12 AM Rose Phillips <RPhillips at linz.govt.nz>
> wrote:
>
>> LAZ files with 129 bits are downloadable for free here :-
>>
>> aws s3 cp s3://pc-bulk/NZ20_Westport/ . --recursive --endpoint-url
>> https://opentopography.s3.sdsc.edu --no-sign-request
>>
>>
>>
>> Using the same pipeline as below I was having the same issue with example
>> file from the above bucket CL2_BR20_2020_1000_4134.laz – output file still
>> contained the 129 bit when explicitly filtered out by writers.las.where
>> statement.
>>
>>
>>
>> *From:* Andrew Bell <andrew.bell.ia at gmail.com>
>> *Sent:* Wednesday, 4 August 2021 11:57 a.m.
>> *To:* Rose Phillips <RPhillips at linz.govt.nz>
>> *Cc:* pdal at lists.osgeo.org
>> *Subject:* Re: [pdal] Attempting to filter out (1) Unclassified points
>> flagged as Withheld
>>
>>
>>
>> The pipeline doesn't seem to match the output you show, so it's hard to
>> know what's going on. If you want to share a file I can see what's up.
>>
>>
>>
>> On Tue, Aug 3, 2021 at 5:22 PM Rose Phillips <RPhillips at linz.govt.nz>
>> wrote:
>>
>> Hi Andrew,
>>
>>
>>
>> Thank you for the heads up, I tried the following pipeline;
>>
>>
>>
>> {
>>
>> "pipeline" : [
>>
>> {
>>
>> "type" : "readers.las",
>>
>> "filename" : "input.las"
>>
>> },
>>
>> {
>>
>> "type" : "writers.las",
>>
>> "a_srs" : "EPSG:2193+7839",
>>
>> "filesource_id" : "0",
>>
>> "filename" : "output.las",
>>
>> "where": "ClassFlags!=129"
>>
>> }
>>
>> ]
>>
>> }
>>
>>
>>
>> However my output LAZ file still had these bits intact;
>>
>>
>>
>> {
>>
>> "file_size": 3007189,
>>
>> "filename": "C:\\Temp\\scan_angle\\test_file\\processed\\
>> CL2_BW24_2020_1000_4526.laz",
>>
>> "now": "2021-08-04T09:20:17+1200",
>>
>> "pdal_version": "2.3.0 (git-version: Release)",
>>
>> "reader": "readers.las",
>>
>> "stats":
>>
>> {
>>
>> "statistic":
>>
>> [
>>
>> {
>>
>> "average": 6.704382019,
>>
>> "count": 1307434,
>>
>> "maximum": 129,
>>
>> "minimum": 2,
>>
>> "name": "Classification",
>>
>> "position": 0,
>>
>> "stddev": 21.69585237,
>>
>> "values":
>>
>> [
>>
>> 2,
>>
>> 3,
>>
>> 4,
>>
>> 5,
>>
>> 7,
>>
>> 9,
>>
>> 18,
>>
>> 129
>>
>> ],
>>
>> "variance": 470.7100099
>>
>> }
>>
>> ]
>>
>> }
>>
>> }
>>
>>
>>
>> Kindest regards Rose
>>
>>
>> *______________________________________________________________________________________________________________________________________________________________*
>>
>> *From:* Andrew Bell <andrew.bell.ia at gmail.com>
>> *Sent:* Tuesday, 3 August 2021 11:00 p.m.
>> *To:* Rose Phillips <RPhillips at linz.govt.nz>
>> *Cc:* pdal at lists.osgeo.org
>> *Subject:* Re: [pdal] Attempting to filter out (1) Unclassified points
>> flagged as Withheld
>>
>>
>>
>>
>>
>>
>>
>> On Mon, Aug 2, 2021 at 5:39 PM Rose Phillips <RPhillips at linz.govt.nz>
>> wrote:
>>
>> Hi pdal’ers
>>
>>
>>
>> These are my attempts to filter out (1) Unclassified Points flagged as
>> withheld in LAS filers for further analyses.
>>
>> Any chance you guys can point to where I have gone wrong?
>>
>>
>>
>> pipelines I have tried using pdal 2.3.0: to filter out (1) unclassified
>> points flagged as withheld;
>>
>>
>>
>> 1.
>>
>>
>>
>> {
>>
>> "pipeline" : [
>>
>> {
>>
>> "type" : "readers.las",
>>
>> "filename" : "input.las"
>>
>> },
>>
>> {
>>
>> "type":"filters.range",
>>
>> "limits":"Classification![129:129]"
>>
>> },
>>
>> {
>>
>> "type" : "writers.las",
>>
>> "a_srs" : "EPSG:2193+7839",
>>
>> "filesource_id" : "0",
>>
>> "filename" : "output.las"
>>
>> }
>>
>> ]
>>
>> }
>>
>>
>>
>> I think that this should filter out unclassified withheld points with LAS
>> 1.2 and 1.3. With LAS 1.4, the withheld attribute is stored in the
>> "ClassFlags" dimension, so you'll need to use boolean logic with that
>> dimension and the "Classification" dimension to do what you want. You might
>> also use pdal info --enumerate to make sure that your data has the values
>> you think it does.
>>
>>
>>
>> --
>>
>> Andrew Bell
>> andrew.bell.ia at gmail.com
>>
>>
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>>
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>>
>>
>>
>> --
>>
>> Andrew Bell
>> andrew.bell.ia at gmail.com
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--
Andrew Bell
andrew.bell.ia at gmail.com
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