{
    "pipeline": [
        {
            "type":"readers.las"
        },
        {
            "type": "filters.reprojection"
        },
        {  
            "type": "filters.smrf"
        },
        {
            "type":"filters.expression",
            "expression":"Classification == 2"
        },
        {
            "gdaldriver":"GTiff",
            "output_type":"idw",
            "resolution" :"2.0",
            "type": "writers.gdal"
        }
    ]
}