[pdal] Filtering atmospheric noise

[Andreas Yankopolus]

All—

I’m using USGS 3DEP point-clouds to generate surface-height rasters around Longmont, CO. The point-cloud files have spurious returns over many of the lakes/reservoirs in the area that are tagged other than 7 or 18. They’re streaks about 0.3 m long located 200+ m above the lake. In most cases the streak has 3–8 points, but I’ve found one with 34 points.

The outlier filter with statistical or radius methods doesn’t remove these longer streaks. Any recommendations on removing dense groups of points well separated from the main mass?

I’m having success with:

{
"type": "filters.outlier",
"method": "radius",
"radius": 16.0,
"min_k": 64
}

This seems to do the trick of removing isolated groups while leaving the main body of points alone, but I’m thinking these some other dimension that could be calculated and added to points then used to remove outlier groups later.

Cheers,

Andreas
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