openmaptiles/layers/transportation_name/transportation_name.yaml

layer:
  id: "transportation_name"
  description: |
      This is the layer for labelling the highways. Only highways that are named `name=*` and are long enough
      to place text upon appear. The OSM roads are stitched together if they contain the same name
      to have better label placement than having many small linestrings.
      For motorways you should use the `ref` field to label them while for other roads you should use `name`.
  buffer_size: 8
  srs: +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over
  fields:
    name: The OSM [`name`](http://wiki.openstreetmap.org/wiki/Highways#Names_and_references) value of the highway.
    ref: The OSM [`ref`](http://wiki.openstreetmap.org/wiki/Key:ref) tag of the motorway or road.
    ref_length: Length of the `ref` field. Useful for having a shield icon as background for labeling motorways.
    network: The OSM [`network`](http://wiki.openstreetmap.org/wiki/Key:network) tag of the road.
    class:
      description: |
          Distinguish between more and less important roads.
      values:
      - motorway
      - trunk
      - primary
      - secondary
      - tertiary
      - minor
      - service
      - track
      - path
      - raceway
      - rail
      - transit
  datasource:
    geometry_field: geometry
    srid: 900913
    query: (SELECT geometry, name, ref, ref_length, class::text FROM layer_transportation_name(!bbox!, z(!scale_denominator!))) AS t
schema:
  - ./merge_highways.sql
  - ./layer.sql
datasources:
  - type: imposm3
    mapping_file: ../transportation/mapping.yaml