[pdal] LAS Files Reclassifying Points with Flags - pdal info query + differences between pdal info / lasinfo classification outputs
Connor Manning
connor at hobu.co
Wed Feb 12 14:03:02 PST 2020
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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