In the Azure map visual in Power BI you can add a reference layer to provide detailed information about regions in the map. In the example below, I've added a reference layer to show census boundaries in the UK:

The Azure maps ability to host reference layers is fantastic but finding those layers can be a nightmare! In this blog I'll show you how to find and download map data and apply it as a reference layer to an Azure map.

Finding reference layer data

The Open Geography Portal is a great source of data and reference layers to choose from.

For this blog, I'm going with the Census and Related Boundaries | Census Boundaries | Lower layer Super Output Areas | 2021 Boundaries map.

Click the name of the map that you are interested in to view it, there are normally several older versions available.

This map covers census boundaries data within the UK.

The website will load a preview of the map so that you can see the data it contains.

Filtering a map

You can apply filters to a map to reduce the amount of data you'll download.

In the diagram below I can see the entire UK, but that's a bit much! I'd like to focus on the Greater Manchester area.

On the right hand side of the Filters pane, click the funnel icon to apply a filter.

Azure Maps supports 30,000 data points and this dataset has 35,672, argh!

Choose which fields you would like to use in the filter by checking boxes in the Select attribute filters list.

To filter by the name of a region, check the box next to LSOA21NM and then type the region name in the search box.

If you have lots of regions to add, filtering by the name would take a long time as you can only add one at a time.

Names work best on smaller data sets.

It's quicker to filter using the Lat and Long properties, either by using the sliders or entering the values directly.

Dragging the slider will update the map in real time, making it easier to choose the right area.

Downloading a map

After applying your filters, you can download the map by clicking on the download button beneath the filter icon.

Bookmark the page if you don't want to recreate filters, especially if you entered them by hand!

On the next page, it will default to downloading the entire dataset, not your filtered version. Click the Toggle Filters option to apply the filters you've created.

Make sure to toggle the filters back on!

You can download the geometry data for the map in a variety of formats. For this example, we'll use the Shapefile format which returns a .zip file type. Click the Download button in the Shapefile box to download it.

Other supported options include GeoJSON, KML and CSV.

We also need the CSV file containing the data we will visualise. Click the Download button in the CSV box to download it.

Download the CSV file as well.

Importing the data in Power BI

Back in Power BI, import the map data by choosing Home | Get data | Text/CSV from the ribbon.

Power BI supports a range of delimiters when importing from a text file.

Choose the csv file you downloaded and click Open to import it.

Consider renaming your files to something a bit snappier!

Applying a reference layer to a map

Next, create an Azure maps visual in Power BI.

Choose to insert an Azure maps visual.

Add the main column from the csv file into the visual. This will be the column containing the data in the csv data source and the zip file containing our reference layer.

You can safely rename the column in the visual, as this is an alias.

To add the reference layer to the map, in the Format visual pane, expand Reference layer | Data source | Upload a file and click Browse...

I've also toggled off the Marker layer. You can keep it on if you like but for this example I don't want it.

Choose the zipped ShapeFile we downloaded earlier and click Open.

Shapefiles will appear as ZIP files.

As long as the names in the CSV and Shapefiles match, after a few seconds the reference layers will render onto the map.

Now apply some formatting and enjoy the results.