[pdal] Ferry filter not working in LAZ file

[Eric Robeck]

Hello,

I have written a PDAL pipeline to perform the following steps:

1.) Ferry the existing Classification to the UserData field for storage
(this is more efficient than creating a new field)
2.) Use the ferry filter to create a new DTM field
3.) Use the colorize filter to extract the elevation value from a
single-band TIF (a DTM made from the original ground points)
4.) Run SMRF to reclassify the ground points

I cannot get the ferry filter to work at all. It won't transfer values
between existing columns or create new columns, despite using the same
syntax described on PDAL.io. I have tried various ways to get around this
issue. Changing the order of filters.ferry in the pipeline didn't make a
difference. I saw that the online examples worked on uncompressed LAS
files, so I converted the input files from LAZ to LAS but there was no
change. The pipeline completes without errors, but info --stats and info
--schema show that the ferried fields were not created or updated.

The colorize filter works fine, as long as I use an existing field. For
example, "dimensions":"Red:1:1000.0" works by mapping the elevation values
to the Red field and multiplying by 1000 to preserve millimeter precision
in an integer field. However, "dimensions":"DTM:1:1000.0" does not, because
the ferry filter doesn't create the DTM field. The SMRF filter also works
well, but without the ability to ferry values I lose the original
classifications.

I am using PDAL 1.6.0 on Windows within OSGeo4W. It was installed this
month. My pipeline is copied below.

Any help would be greatly appreciated.

Thanks,
Eric


{
  "pipeline":
  [
    "C:/data/forest_park/filtered/forest_park_orig.laz",
    {
      "type":"filters.ferry",
      "dimensions":"Classification=>UserData, =>DTM"
    },
    {
      "type":"filters.colorization",
      "dimensions":"DTM:1:1000.0",
      "raster":"C:/data/forest_park/dtm/w001001.adf"
    },
    {
      "type":"filters.smrf",
      "cell":1.00,
      "cut":0,
      "scalar":1.25,
      "slope":0.00,
      "threshold":0.50,
      "window":10
    },
    {
      "type":"writers.las",
      "tag":"writerslas",
      "compression":"true",
      "scale_x":"0.01",
      "scale_y":"0.01",
      "scale_z":"0.01",
      "offset_x":"auto",
      "offset_y":"auto",
      "offset_z":"auto",
      "filename":"C:/data/forest_park/forest_park_orig_dtm.laz"
    }
  ]
}
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