lasground with buffered

[REHÁNY Nikolett (BKK Közút)]

Hello,

I use lastools for my work on classified mobile laser scanned pointcloud.
There is a step in our classifying workflow where the ground is refined with this command:

c:\lastools\bin\lasground.exe -i d:\tile\*.laz ^
        -ignore_class 1 7 25 -cores 4 -step 1 ^
        -extra_fine -no_stddev -spike 0.1 -offset 0.01 ^
        -ground_class 11 -non_ground_class 2 ^
        -buffered 2 -odir d:\ground -olaz

It usually works perfectly but sometimes leaves out a tile. When I run the command without '-buffered' it creates all grounded tiles.

I uploaded a part of the pointcloud (https://drive.google.com/file/d/0B8ULdo4l3_Lob005WG40Ti1QQW8/view?usp=sharing), 654560_232384_32.laz is the problematic file in this sample. (It contains 18.7 million points.)
Could you help me find out what is the problem?

Best regards,
Nikolett

 

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[Martin Isenburg]

Hello,

you will likely exceed the maximum number of points if your 32 by 32 meter tile already has 18.7 million points and you are adding a buffer of 2 meters in each direction using the points from the neighboring tiles.

I suggest to run lastile with option '-refine_tiling 10000000' a few times to assure no tile has more than 10000000 points. In your case, simply add a few calls like this before lasground. Note that each call does only one level of refinement (e.g. 32 by 32 sized tiles with 18.7 million points are split into four tiles of 16 by 16  (no matter how many points each 16 by 16 tile contains).

Also ... it may be more efficient to add the 2 meter buffer in the initial run of lastile already. Then you always know exactly how big the buffered tiles will be. Running lastile with option '-refine_tiling 10000000' on tiles with buffer will count the points from the buffer as well and also preserve buffers.

lastile -i d:\tile\*.laz ^

         -refine_tiling 10000000 ^

          -cores 4

lastile -i d:\tile\*.laz ^

         -refine_tiling 10000000 ^

          -cores 4

lastile -i d:\tile\*.laz ^

         -refine_tiling 10000000 ^

          -cores 4

Regards,

Martin @rapidlasso

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[REHÁNY Nikolett (BKK Közút)]

Hello,

it works. Thank you!

Best regards,
Nikolett

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Feladó: last...@googlegroups.com [last...@googlegroups.com] ; meghatalmazó: Martin Isenburg [martin....@gmail.com]
Küldve: 2015. április 25. 21:38
Címzett: LAStools - efficient command line tools for LIDAR processing
Tárgy: Re: [LAStools] lasground with buffered