.. _vector_tiles:

Vector tiles
============

To serve vector tiles you need to define a grid under key ``vector_tiles`` in ``geoportal/vars.yaml``, example:

.. code:: yaml

    vars:
      vector_tiles:
        srid: 2056
        extent: [2420000, 1030000, 2900000, 1350000]
        resolutions: [4000, 2000, 1000, 500, 250, 100, 50, 20, 10, 5, 2.5, 1, 0.5, 0.25, 0.1, 0.05]

And to build the layer on the ngeo side, you must use the same parameters under key
``interfaces_config.default.constants.gmfVectorTilesOptions``. The projection and the tileGrid must match
the map parameters:

.. code:: yaml

    vars:
      interfaces_config:
        default:
          gmfVectorTilesOptions:
            projection: EPSG:2056
            tileGrid: <Open layers ol/tilegrid/TileGrid options>

You also need to define at least one "Vector Tiles" layer in admin interface with the following required attributes:

name
   Name of the layer

style
   URL to a Mapbox Style file (version 8 or higher), examples:
   - https://example.com/mystyle.json
   - static:///mb_styles/osm_landuse.json

sql
   PostGIS SQL query template with ``{envelope}`` parameter.

For example, for considered table:

.. code:: sql

   CREATE TABLE geodata.osm_landuse (
       fid integer NOT NULL,
       osm_id bigint,
       name character varying(48),
       type character varying(16),
       geom public.geometry(Polygon,2056)
   );

Here is an example SQL query template:

.. code:: sql

    SELECT ST_AsMVT(q, 'osm_landuse') FROM (
        SELECT
            fid,
            osm_id,
            name,
            type,
            ST_AsMVTGeom("geom", <envelope>) as geom
        FROM geodata.osm_landuse
        WHERE ST_Intersects("geom", <envelope>)
    ) AS q

Then your vector tiles will be accessible, for example in local development mode, through:

https://localhost:8484/vector_tiles/{layer_name}/{z}/{x}/{y}.pbf

.. note::

   Currently vector tiles layers in GMF have a limited support. A vector tiles layer can be only
   added as a background layer. It's not possible to print it and it doesn't support dimensions.
   Queries can be only done via another WMS layer using the metadata ``ogcServer`` and ``queryLayers``.