las2las Filter RGB values

[Karin...@ldbv.bayern.de]

Hello,

 

I try to detect buildings in a point cloud from image matching.

I want to use the color info as additional input.

 

las2las has some options to keep RGB values in a certain range.

What is missing, is to drop RGB values in a range or to drop values below/above a certain limit.

Maybe this is already implemented and I just missed it?

 

 

Thanks

Karin

 

 

 

[Martin Isenburg]

Hello,

you can have a look at the open source code of LASlib that implements the LASfilter class in charge for all those '-keep_ ... ' and '-drop_....' options.

https://github.com/LAStools/LAStools/blob/master/LASlib/src/lasfilter.cpp#L1782

what new filters would you need. Can you describe how you would expect them to work and what parameters they should accept? An example is always helpful ... (-:

Regards.

Martin

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[Karin...@ldbv.bayern.de]

Hello,

 

up to now I do the RGB filtering with a script like this:

 

las2las  -i tiles_1000_RGB3\*_class.la* ^         

-keep_RGB_red 20000 65025 ^              

-keep_RGB_green 45000 65025 -filter_and ^

-keep_RGB_blue 35000 65025 -filter_and ^ 

-keep_NDVI_intensity_is_NIR -1.0 0.3 ^   

-cores 6 ^                               

-odir tiles_1000_RGB3 ^                  

-odix _int ^                             

-olaz                                    

 

I want to do more testing since the RGB values of point clouds from image matching are different depending on the flight.

 

I want to keep values R < 5000 and R > 20000 eg.

I think the script then has to look like this (I did not test it):

 

las2las  -i tiles_1000_RGB3\*_class.la* ^         

-keep_RGB_red 0 4999 ^

-keep_RGB_red 20001 65025 ^ -filter_and ^            

-keep_RGB_green 45000 65025 -filter_and ^

-keep_RGB_blue 35000 65025 -filter_and ^ 

-keep_NDVI_intensity_is_NIR -1.0 0.3 ^   

-cores 6 ^                               

-odir tiles_1000_RGB3 ^                  

-odix _int ^                             

               -olaz

 

 

I would expect a filter to drop certain ranges of values:

                                  

las2las  -i tiles_1000_RGB3\*_class.la* ^         

-drop_RGB_red 5000 20000 ^              

-keep_RGB_green 45000 65025 -filter_and ^

-keep_RGB_blue 35000 65025 -filter_and ^ 

-keep_NDVI_intensity_is_NIR -1.0 0.3 ^   

-cores 6 ^                               

-odir tiles_1000_RGB3 ^                  

-odix _int ^                             

               -olaz                                    

 

 

Anyway, using RGB values is very tricky since I do not now the color space of roofs (sometimes they are grey, green roofs…).

Additionally I try to use the height above ground. Data from image matching is rather noisy, so I can rarely use planarity.

 

Regards

Karin

[Martin Isenburg]

Hello,

the latest version of LAStools (180520) that can be downloaded from

http://rapidlasso.com/LAStools

has some new filters that have the requested functionality such as

-drop_RGB_red 1000 5000

-drop_RGB_green 200 10000

-drop_RGB_blue 0 1000
-drop_RGB_nir 2000 4000 

Regards,

Martin @rapidlasso