# filters.smrf

Filter ground returns using the Simple Morphological Filter (SMRF) approach outlined in [Pingel2013].

[Pingel2013] | Pingel, T.J., Clarke, K.C., McBride, W.A., 2013. An improved simple morphological filter for the terrain classification of airborne LIDAR data. ISPRS J. Photogramm. Remote Sens. 77, 21–30.

Default Embedded Stage

This stage is enabled by default

## Example

The sample pipeline below uses `filters.smrf` to segment ground and non-ground returns, writing only the ground returns to the output file.

    {
      "pipeline":[
        "input.las",
        {
          "type":"filters.smrf"
        },
        {
          "type":"filters.range",
          "limits":"Classification[2:2]"
        },
        "output.laz"
      ]
    }

## Options

cell
  Cell size. [Default: 1.0]
cut
  Cut net size (`cut=0` skips the net cutting step). [Default: 0.0]
dir
  Optional output directory for debugging intermediate rasters.
scalar
  Elevation scalar. [Default: 1.25]
slope
  Slope (rise over run). [Default: 0.15]
threshold
  Elevation threshold. [Default: 0.5]
window
  Max window size. [Default: 18.0]