# filters.overlay

The overlay filter allows you to set the values of a selected dimension based on an OGR-readable polygon or multi-polygon.

Default Embedded Stage

This stage is enabled by default

## OGR SQL support

You can limit your queries based on OGR’s SQL support. If the filter has both a datasource and a query option, those will be used instead of the entire OGR data source. At this time it is not possible to further filter the OGR query based on a geometry but that may be added in the future.

Note

The OGR SQL support follows the rules specified in ExecuteSQL documentation, and it will pass SQL down to the underlying datasource if it can do so.

## Example 1

In this scenario, we are altering the attributes of the dimension ‘Classification’. Points from autzen-dd.las that lie within a feature will have their classification to match the ‘CLS’ field associated with that feature.

    {
      "pipeline":[
        "autzen-dd.las",
        {
          "type":"filters.overlay",
          "dimension":"Classification",
          "datasource":"attributes.shp",
          "layer":"attributes",
          "column":"CLS"
        },
        {
          "filename":"attributed.las",
          "scale_x":0.0000001,
          "scale_y":0.0000001
        }
      ]
    }

## Example 2

This example sets the Intensity attribute to `CLS` values read from the OGR SQL query.

    {
      "pipeline":[
        "autzen-dd.las",
        {
          "type":"filters.overlay",
          "dimension":"Intensity",
          "datasource":"attributes.shp",
          "query":"SELECT CLS FROM attributes where cls!=6",
          "column":"CLS"
        },
        {
          "filename":"attributed.las",
        }
      ]
    }

## Options

dimension
  Name of the dimension whose value should be altered. [Required]
datasource
  OGR-readable datasource for Polygon or MultiPolygon data. [Required]
column
  The OGR datasource column from which to read the attribute. [Default: first column]
query
  OGR SQL query to execute on the datasource to fetch geometry and attributes. The entire layer is fetched if no query is provided. [Default: none]
layer
  The data source’s layer to use. [Defalt: first layer]