How to add a polygon reference layer to the map

The reference layer feature provides a way to consistently display administrative polygons/boundaries (e.g. LSOAs, wards, etc.) regardless of how point data is filtered on the page.

Custom geometry

This only works for ONS GSS codes and boundaries (e.g. W00008779). Other geometries are not supported by the reference layer, but you can add these by uploading your own data instead and displaying them as unmatched features.

The reference layer feature can be found under the Visualisations pane > Format Visual > Reference Layer Settings

For a reference layer to be generated, the relevant GSS codes need to be input into the ‘GSS Codes for Reference Layer’ text box.

GSS codes can be copied and pasted directly from a spreadsheet into the text box, and it will automatically work.

A screenshot of the Reference Layer pane

Once the codes have been input, the visual should update after a few seconds with the relevant polygons displayed on the map as a reference layer that is not linked to any other data used in the visual.

Good to know

• The codes added to the GSS Codes for Reference Layer textbox will be sent out of the visual to services maintained by the Office for National Statistics, in order to retrieve the geometries.

• The values you add are checked first to make sure they fit the format of a GSS code (a letter followed by 8 numbers). Any data mistakenly added to this textbox that doesn't match the format won't be sent out of the visual, to prevent inadvertent data loss.

• This feature makes use of the services published by the ONS Open Geography Portal and is subject to the availability and currency of those services. Should the services be unavailable, then the visual will not be able to retrieve the geometries.

You can then style the reference layer features using the appropriate dropdown under the Symbology Settings pane:

Symbology settings pane

Note that if you are using GSS codes to populate the map's Feature Layer using ONS geographies, the codes that are entered into the Reference Layer dialog will be compared to the codes which are currently displayed in the Feature Layer, and any polygons which are currently being shown in the Feature Layer will not also be displayed in the Reference Layer.

This allows you to create a background in the reference layer which continually updates as slicers / filters are applied to the Feature Layer. However this only works for codes that match exactly; geographies from different overlapping datasets (e.g. MSOA vs LSOA) will not be compared and updated in this way.

Historic ONS GSS codes

Not all types of GSS code are necessarily supported for the reference layer. The visual makes use of services that are published in the ONS Open Geography Portal.

These are subject to change from time to time by ONS. The visual may be reconfigured to show new services as we are made aware of them. The table in the FAQs tab of the "Getting Started" dialog tells you which codes are currently supported.

The visual will only support the latest version of geometries for any particular code type. Historic codes are unfortunately NOT supported at this time.