Mon 05 September 2022

Web Mercator OS Vector Tile API in OpenLayers - Take #2

This is an update to my previous post on the same subject.

Thanks to some feedback from Andreas Hocevar and a pull request I made to ol-mapbox-style adding a Vector Tile layer of Ordnance Survey data from the OS Data Hub to an OpenLayers map in Web Mercator is a little easier than it was a few months ago 🎉

The following uses create-ol-app to create a basic OpenLayers app, we then add the ol-mapbox-style package and install the other dependencies:

# Create a new OpenLayers app in a folder called os-vt-api-ol
npx create-ol-app os-vt-api-ol

# Change to the newly created folder which contains our app
cd os-vt-api-ol/

# Install the ol-mapbox-style package from npm
npm i ol-mapbox-style

# Install the other dependencies (vite and ol)
npm i

# Start the vite local web server which reloads during development (see the "start" script in package.json)
npm start

Next update the code to add the OS Vector Tile layer:


import './style.css';
import { Map, View } from 'ol';
import VectorTileLayer from 'ol/layer/VectorTile';
import { transform } from 'ol/proj';
import { applyStyle } from 'ol-mapbox-style';


let OsVtLyr = new VectorTileLayer({
  declutter: true,

  '' +
    // Specify the optional transformRequest function which is
    // called before each resource associated with the style
    // is fetched. In this instance we are ensuring the `srs`
    // parameter is set to `3857` (Web Mercator) when fetching
    // each resource (Source, Sprite, Tiles etc.). Full docs at
    transformRequest(url, type) {
      url = new URL(url);
      if (!url.searchParams.has('srs')) {
        url.searchParams.append('srs', '3857');
      return new Request(url);
).then((e) => {
  // Once the style has been applied set the attribution which is missing
  // from the source document
      '&copy; <a href="">Ordnance Survey</a>'

const map = new Map({
  target: 'map',
  layers: [OsVtLyr],
  view: new View({
    center: transform([-2.333029, 52.109524], 'EPSG:4326', 'EPSG:3857'),
    zoom: 14,

See the comments in the code for an explanation of the steps involved. The you should end up with a map that looks something like this:

OpenLayers map showing styled OS Vector Tiles data for Malvern, UK