Using Whitebox plugin in QGIS

Question

QGIS 3.8.3 running in Ubuntu 18.04.3 LTS

I've installed Whitebox Tools and the Whitebox plugin and am able to obtain, for example, data on a .las file using 'Lidarinfo', so the system appears to be working (at least at this level).

However, attempting to use LidarNearestNeighbourGridding produces the following:

Algorithm 'LidarNearestNeighbourGridding' starting… Input parameters: { 'exclude_cls' : '1,3,4', 'input' : '/home/nick/Desktop/SU5771_P_9194_20131130_20131201.las', 'maxz' : None, 'minz' : None, 'output' : '/home/nick/Desktop/SU5771_P_9194_20131130_20131201.tif', 'parameter' : 0, 'radius' : 2.5, 'resolution' : 1, 'returns' : 0 }

WhiteBoxTools command: "/home/nick/whitebox_tools/WBT/whitebox_tools" --run=LidarNearestNeighbourGridding --input="/home/nick/Desktop/SU5771_P_9194_20131130_20131201.las" --parameter="elevation" --returns="all" --resolution=1.0 --radius=2.5 --exclude_cls="1,3,4" --minz=0.0 --maxz=0.0 --output="/home/nick/Desktop/SU5771_P_9194_20131130_20131201.tif" -v WhiteBoxTools command output:

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• Welcome to LidarNearestNeighbourGridding *

---

Performing interpolation...

Reading input LAS file...

No points found in /home/nick/Desktop/SU5771_P_9194_20131130_20131201.las

Finished interpolating homenickDesktopSU5771_P_9194_20131130_20131201 (1 of 1)

Elapsed Time (including I/O): 0.146s

Execution completed in 0.29 seconds Results: {'output': }

Loading resulting layers The following layers were not correctly generated.

• /home/nick/Desktop/SU5771_P_9194_20131130_20131201.tif

You can check the 'Log Messages Panel' in QGIS main window to find more information about the execution of the algorithm.

"No points found in /home/nick/Desktop/SU5771_P_9194_20131130_20131201.las" would appear to be the operative part of this.

The file is a UK Environment Agency .laz file unzipped using laszip and was supplied already classified.

I'm very new to processing lidar data but I have produced DTMs using LAStools and also using PDAL.

Am I missing something here?

Answer 1

I do not know the plugin or its code, but this part of the command attracts attention:

--minz=0.0 --maxz=0.0

It is probably not the expected behavior, but the algorithm seems to be filtering the input points to interpolate only among those that have a height equal to zero.

Try to establish specific values, within the range of heights of your source data, to be assigned to the minz and maxz parameters of the point filter to be interpolated.