Serve and Export Vector Tiles from PostGIS

In this tutorial, we'll learn how to create vector tiles from the data imported into PostGIS.

If you have not yet inserted data into your PostGIS database, please follow one of these three guides:

If you are in a hurry, consider skipping the "Under the Hood" sections.

Creating Vector Tiles

In order to create vector tiles, Apache Baremaps requires JSON configuration files. The two configuration files used are:

tileset.json - Defines all the information needed to retrieve the correct vector tile layers at different zoom levels.
style.json - Defines the style of the different layers.

For convenience, we have prepared a tileset.json and a style.json that correspond to each of the examples.

Each of these files are available in the main repository of Apache Baremaps inside the examples' folder.

First cd into one of the example directories that corresponds to the data you inserted inside your PostGIS database. Then let's preview and edit the map with the sample configuration files by executing the following command in a terminal.

baremaps map dev \
  --tileset 'tileset.json' \
  --style 'style.json'

Well done, a local development server should have started. You can now visualize the vector tiles in your browser (http://localhost:9000/)! Notice that the changes in the configuration files are automatically reloaded by the browser.

Under the Hood (Optional)

Baremaps extensively rely on the fantastic ST_AsMVT (opens in a new tab) functions released by the PostGIS team to produce Mapbox Vector Tiles (opens in a new tab). However, in the following excerpt of the json configuration file, none of these concepts appear in the SQL queries.

{
  ...
  "vector_layers": [
    {
      "id": "aeroway",
      "queries": [
        {
          "minzoom": 12,
          "maxzoom": 20,
          "sql": "SELECT id, tags, geom FROM osm_nodes WHERE tags ? 'aeroway'"
        },
        ...
      ]
    },
  ],
  ...
}

Why don't we see these function calls in the configuration? Baremaps wants you to focus on the content of the tiles, and relieves you from the burden of writing complex SQL queries. In fact, at runtime, Baremaps merges all the queries of the configuration file into a single optimized query that produces vector tiles.

In production, vector tiles are rarely served dynamically. Why is that so? First, a large blob store is much cheaper than a relational database to operate (opens in a new tab). Second, content delivery networks (CDNs) greatly improve web performances by caching static content close to the end user. Baremaps has been conceived with these lasting trends in mind. The following command produces a local directory containing precomputed static tiles. These tiles can be served with Apache, Nginx, or Caddy, but also copied in a blob store behind a content delivery network, such as Cloudflare, Stackpath, or Fastly.

baremaps map export \
  --tileset 'tileset.json' \
  --repository 'tiles/'

Conclusion

In this tutorial, we learnt how to create vector tiles from PostGIS data with the help of Apache Baremaps. Prior to the release of Apache Baremaps, we believe that creating a pipeline for publishing vector tiles from OpenStreetMap data was a rather time-consuming task. As shown in this demonstration, Apache Baremaps tries to bring back the fun to creating a web mapping pipeline!

Import OpenStreetMap into PostGIS Contour Lines in Vector Tiles