# filters.dem

The DEM filter uses a source raster to keep point cloud data within a each cell within a computed range. For example, atmospheric or MTA noise in a scene can be quickly removed by keeping all data within 100m above and 20m below a preexisting elevation model.

Default Embedded Stage

This stage is enabled by default

## Example

    [
        {
            "type":"filters.dem",
            "raster":"dem.tif",
            "limits":"Z[20:100]"
        }
    ]

## Options

limits

  A range that defines the dimension and the magnitude above and below the value of the given dimension to filter.

  For example “Z[20:100]” would keep all `Z` point cloud values that are within 100 units above and 20 units below the elevation model value at the given `X` and `Y` value.

raster

  GDAL readable raster data to use for filtering.

band

  GDAL Band number to read (count from 1) [Default: 1]

where

  An expression that limits points passed to a filter. Points that don’t pass the expression skip the stage but are available to subsequent stages in a pipeline. [Default: no filtering]

where_merge

  A strategy for merging points skipped by a ‘where’ option when running in standard mode. If `true`, the skipped points are added to the first point view returned by the skipped filter. If `false`, skipped points are placed in their own point view. If `auto`, skipped points are merged into the returned point view provided that only one point view is returned and it has the same point count as it did when the filter was run. [Default: `auto`]