treetop extraction

gistfile1.txt

[
    {
        "type": "readers.las",
        "filename": "/Users/hobu/dev/git/pdal-data/autzen/new/autzen-classified.copc.laz"
    },
    {
        "type": "filters.hag_nn"
    },
    {
        "type": "filters.assign",
        "value": [
            "MaybeTreeTops = 1"
        ],
        "where": "ReturnNumber == NumberOfReturns && NumberOfReturns > 1 && HeightAboveGround > 1.5"
    },
    {
        "type": "writers.copc",
        "extra_dims": "all",
        "filename": "forest-autzen.copc.laz"
    }
]