How to create a choropleth Map from GeoJSON using OpenLayers

This tutorial shows how to add a styled GeoJSON overlay to the map, display a popup on click, and create a map legend. As an example data, we use countries with attributes from EUROSTAT in GeoJSON format. Download the sample data here

  1. Copy the following code, paste it into your favorite text editor, and save it as a .html file.

  2. Replace YOUR_MAPTILER_API_KEY_HERE with your actual MapTiler API key.

  3. The next it’s up to you. You can start the map in a different place by modifying the starting position and starting zoom, and you can change the look of the map to any of our styles, or yours, by updating the source URL. See what’s available here.

  4. Add the GeoJSON layer. The following snippet creates GeoJSON layer hosted on MapTiler Cloud (check out the How to Upload GeoJSON to MapTiler Cloud tutorial). The GeoJSON used in the example contains data from Eurostat Marriage indicators dataset filtrated to just countries with some value of mean age of women at first marriage in 2019. Download the sample data here

  5. Create the functions to get the style based on the age attribute.

  6. Create a choropleth map based on the age attribute. Change the style property of the layer.

  7. Create the popup html element.

  8. Create the style for the popup

  9. Create the overlay to anchor the popup

  10. Add the overlay to the map

  11. Create a function to display a popup when clicking on the geojson layer and show the information of the age attribute
  12. Create a map legend.

  13. Create the style for the map legend.

Learn more

Get more details about this tutorial on Zoomable Choropleth Map from GeoJSON with OpenLayers or check out the following How-tos related to choropleth maps

How to style a choropleth map in Edit Tool

Prepare GeoJSON with attributes for choropleth map and upload GeoJSON to MapTiler Cloud