Adding classification to points

[Tobias Wittwer]

Hi,

 Is there a lastools command that makes it possible to add classification to the points in a LAZ file, from a text file that holds the classes in the same order as the points in the LAZ? I’ve taken a look at the documentation of las2las and txt2las and couldn’t find a command that would do this.

 Regards,

Tobias

[Martin Isenburg]

Hello Tobias,

excellent question. There is no direct tool but there is a way. Let's first create some sample data:

:: create a 'fusa.laz' version with zeroed classifications

las2las -i ..\data\fusa.laz -set_classification 0 -o fusa_class_zeroed.laz

:: create a TXT file with classifications in the same order as points
las2txt -i ..\data\fusa.laz -parse c -o fusa_class.txt

Now first let's turn the TXT file also into a LAZ file.

txt2las -i fusa_class.txt -parse c -o fusa_class.laz

You might want to check that the number of points and the histogram of classification codes are as expected:

lasinfo -i fusa_class.laz

Now use this version of lascopy that has the new option '-unmatched' activated.

https://www.dropbox.com/s/cpqzfmq9hfpf7h4/lascopy.exe

And run this command with the new '-unmatched' switch that disables the check for identical "GPS time" and "return number"  between source and target that is usually used before a point attribute (which by default are the classification codes) is copied.

lascopy -i fusa_class.laz -i fusa_class_zeroed.laz -unmatched -o fusa_recovered.laz

And voila ... the classifications are back:

lasview -i fusa_class_zeroed.laz
lasview -i fusa_recovered.laz

This will be in the next LAStools release ... (-:

Regards,

Martin

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[Tobias Wittwer]

Very helpful, thanks!

Op maandag 31 mei 2021 om 13:41:04 UTC+2 schreef martin....@gmail.com: