[pdal] LAS Files Reclassifying Points with Flags - pdal info query + differences between pdal info / lasinfo classification outputs
Bradley Chambers
brad.chambers at gmail.com
Wed Feb 12 14:39:07 PST 2020
Correct, your pipeline is reclassifying non-withheld rail (10) as
non-withheld bridge (17). It is leaving the withheld rail (138) untouched.
This may be confusing in a couple of ways. First, lasinfo shows that you
have withheld points but it doesn’t provide a breakout in the individual
point counts. Also, the PDAL output just shows withheld points with their
bit shifted values, which may not be obvious. I think all reports you are
running are in fact giving you the correct information for the pipeline you
provided.
On Wed, Feb 12, 2020 at 17:03 Connor Manning <connor at hobu.co> wrote:
> Regarding the Classification assignment, I think you've got the filter
> specification backwards. To "reclassify points under code 17 to 10", you
> would want "assignment":"Classification[17:17]=10".
>
> On Wed, Feb 12, 2020 at 3:48 PM Rose Phillips <RPhillips at linz.govt.nz>
> wrote:
>
>> Hi guys,
>>
>>
>>
>> Hope you’re all having a good week.
>>
>> When reclassifying points in LAS files where there are also flags
>> (withheld, synthetic, keypoint or overlap), I’ve noticed a discrepancy
>> between pdal info + lasinfo reports with my output LAS files, and an
>> assortment of classification codes (for pdal info) that I’m not familiar
>> with.
>>
>>
>>
>> I used pdal pipeline to reclassify points under code 17 to 10 :-
>>
>>
>>
>>
>>
>> {
>>
>> "pipeline" : [
>>
>> {
>>
>> "type" : "readers.las",
>>
>> "filename" : "input.las"
>>
>> },
>>
>> {
>>
>> "type":"filters.assign",
>>
>> "assignment":"Classification[10:10]=17"
>>
>> },
>>
>> {
>>
>> "type" : "writers.las",
>>
>> "minor_version" : 4,
>>
>> "dataformat_id": 1,
>>
>> "a_srs" : "EPSG:2193+7839",
>>
>> "forward" : "all",
>>
>> "filename" : "output.las"
>>
>> }
>>
>> ]
>>
>> }
>>
>>
>>
>>
>>
>> Looking at lasinfo reports, for an input and output file, it looks like
>> there are still points assigned as 17? But the pdal info reports show
>> something else, and points with different counts e.g.
>>
>>
>>
>> *Input file (pdal info)*
>>
>> * "filename": "D:\\ BM34_2018_1000_1637.las",*
>>
>> * "pdal_version": "2.0.1 (git-version: Release)",*
>>
>> * "stats":*
>>
>> * {*
>>
>> * "statistic":*
>>
>> * [*
>>
>> * {*
>>
>> * "average": 38.90448897,*
>>
>> * "count": 4048726,*
>>
>> * "counts":*
>>
>> * [*
>>
>> * "1.000000/1",*
>>
>> * "2.000000/2590331",*
>>
>> * "3.000000/146834",*
>>
>> * "4.000000/16873",*
>>
>> * "5.000000/106701",*
>>
>> * "6.000000/13937",*
>>
>> * "7.000000/51",*
>>
>> * "9.000000/14124",*
>>
>> * "10.000000/218",*
>>
>> * "130.000000/993308",*
>>
>> * "131.000000/102834",*
>>
>> * "132.000000/6622",*
>>
>> * "133.000000/40561",*
>>
>> * "134.000000/9820",*
>>
>> * "135.000000/5",*
>>
>> * "137.000000/6215",*
>>
>> * "138.000000/291"*
>>
>> * ],*
>>
>> * "maximum": 138,*
>>
>> * "minimum": 1,*
>>
>> * "name": "Classification",*
>>
>> * "position": 0,*
>>
>> * "stddev": 57.89674269,*
>>
>> * "variance": 3352.032814*
>>
>> * }*
>>
>> * ]*
>>
>> * }*
>>
>> *}*
>>
>>
>>
>> *Output File (pdal info)*
>>
>> *{*
>>
>> * "filename":
>> "D:\\palmerston_north_cc\\pdal_reclassification_issue\\reclassified\\CL2_BM34_2018_1000_1637.laz",*
>>
>> * "pdal_version": "2.0.1 (git-version: Release)",*
>>
>> * "stats":*
>>
>> * {*
>>
>> * "statistic":*
>>
>> * [*
>>
>> * {*
>>
>> * "average": 38.90486588,*
>>
>> * "count": 4048726,*
>>
>> * "counts":*
>>
>> * [*
>>
>> * "1.000000/1",*
>>
>> * "2.000000/2590331",*
>>
>> * "3.000000/146834",*
>>
>> * "4.000000/16873",*
>>
>> * "5.000000/106701",*
>>
>> * "6.000000/13937",*
>>
>> * "7.000000/51",*
>>
>> * "9.000000/14124",*
>>
>> * "17.000000/218",*
>>
>> * "130.000000/993308",*
>>
>> * "131.000000/102834",*
>>
>> * "132.000000/6622",*
>>
>> * "133.000000/40561",*
>>
>> * "134.000000/9820",*
>>
>> * "135.000000/5",*
>>
>> * "137.000000/6215",*
>>
>> * "138.000000/291"*
>>
>> * ],*
>>
>> * "maximum": 138,*
>>
>> * "minimum": 1,*
>>
>> * "name": "Classification",*
>>
>> * "position": 0,*
>>
>> * "stddev": 57.8965773,*
>>
>> * "variance": 3352.013663*
>>
>> * }*
>>
>> * ]*
>>
>> * }*
>>
>> *}*
>>
>>
>>
>> *Input file (lasinfo)*
>>
>>
>>
>> histogram of classification of points:
>>
>> 1 unclassified (1)
>>
>> 3583639 ground (2)
>>
>> 249668 low vegetation (3)
>>
>> 23495 medium vegetation (4)
>>
>> 147262 high vegetation (5)
>>
>> 23757 building (6)
>>
>> 56 noise (7)
>>
>> 20339 water (9)
>>
>> 509 rail (10)
>>
>> +-> flagged as withheld: 1159656
>>
>>
>>
>> *Output file (lasinfo)*
>>
>>
>>
>> histogram of classification of points:
>>
>> 1 unclassified (1)
>>
>> 3583639 ground (2)
>>
>> 249668 low vegetation (3)
>>
>> 23495 medium vegetation (4)
>>
>> 147262 high vegetation (5)
>>
>> 23757 building (6)
>>
>> 56 noise (7)
>>
>> 20339 water (9)
>>
>> 291 rail (10)
>>
>> 218 bridge deck (17)
>>
>> +-> flagged as withheld: 1159656
>>
>>
>>
>>
>>
>> I’m guessing pdal info is the most accurate output as arcgis pro + global
>> mapper outputs are the same as pdal info and lasinfo is the odd one out.
>>
>> I wrote a las2las and pdal pipeline workaround to make sure that both
>> lasinfo + pdal info outputs were the same.
>>
>>
>>
>> I was wondering if you guys knew why the flags were written as numbers
>> and why they are split up in codes, that change for each file?
>>
>>
>>
>> Many thanks and kind regards,
>>
>> Rose Phillips
>>
>>
>>
>> Location Data Analyst
>>
>> Land Information New Zealand
>>
>>
>>
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