layer:
  id: "park"
  description: |
      The park layer contains parks from OpenStreetMap tagged with either [`boundary=national_park`](http://wiki.openstreetmap.org/wiki/Tag:boundary%3Dnational_park) or [`leisure=nature_reserve`](http://wiki.openstreetmap.org/wiki/Tag:leisure%3Dnature_reserve).
  buffer_size: 4
  fields:
    class:
      description: |
          Use the **class** to differentiate between different parks.
      values:
      - national_park
      - nature_reserve
  datasource:
    geometry_field: geometry
    query: (SELECT geometry, class FROM layer_park(!bbox!, z(!scale_denominator!))) AS t
schema:
  - ./layer.sql
datasources:
  - type: imposm3
    mapping_file: ./mapping.yaml