# filters.ferry

The ferry filter copies data from one dimension to another, creates new dimensions or both.

The filter is guided by a list of ‘from’ and ‘to’ dimensions in the format <from>=<to>. Data from the ‘from’ dimension is copied to the ‘to’ dimension. The ‘from’ dimension must exist. The ‘to’ dimension can be pre-existing or will be created by the ferry filter.

Alternatively, the format =<to> can be used to create a new dimension without copying data from any source. The values of the ‘to’ dimension are default initialized.

Default Embedded Stage

This stage is enabled by default

Streamable Stage

This stage supports streaming operations

## Example 1

In this scenario, we are making copies of the X and Y dimensions into the dimensions StatePlaneX and StatePlaneY. Since the reprojection filter will modify the dimensions X and Y, this allows us to maintain both the pre-reprojection values and the post-reprojection values.

    {
      "pipeline":[
        "uncompressed.las",
        {
          "type":"readers.las",
          "spatialreference":"EPSG:2993",
          "filename":"../las/1.2-with-color.las"
        },
        {
          "type":"filters.ferry",
          "dimensions":"X = StatePlaneX, Y=StatePlaneY"
        },
        {
          "type":"filters.reprojection",
          "out_srs":"EPSG:4326+4326"
        },
        {
          "type":"writers.las",
          "scale_x":"0.0000001",
          "scale_y":"0.0000001",
          "filename":"colorized.las"
        }
      ]
    }

## Example 2

The ferry filter is being used to add a dimension ‘Classification’ to points so that the value can be set to ‘2’ and written as a LAS file.

    {
      "pipeline":[
        {
            "type": "readers.gdal",
            "filename": "somefile.tif"
        },
        {
            "type": "filters.ferry",
            "dimensions": "=Classification"
        },
        {
            "type": "filters.assign",
            "assignment": "Classification[:]=2"
        },
        "out.las"
      ]
    }

## Options

dimensions
  A list of dimensions whose values should be copied. The format of the option is <from>=<to>, <from>=<to>,… Spaces are ignored. ‘from’ can be left empty, in which case the ‘to’ dimension is created and default-initialized. ‘to’ dimensions will be created if necessary.