> For the complete documentation index, see [llms.txt](https://docs.os.uk/more-than-maps/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/more-than-maps/advanced-applications/os-ngd-data-in-dashboards/os-power-bi-map-visual/os-power-bi-map-visual-faqs.md).
# OS Power BI Map Visual FAQs
How many points / polygons can be displayed on a map?
Power BI allows up to 30 000 individual points and / or polygons to be displayed on a map at any one time. However, attempting to display even this number will likely cause performance issues.
How many layers can be displayed on a map?
The map contains up to two data-driven layers, and optionally a separate reference layer. See the [Adding data to the map page](/more-than-maps/advanced-applications/os-ngd-data-in-dashboards/os-power-bi-map-visual/os-power-bi-map-visual-getting-started-guide/adding-data-to-the-map.md#core-concepts) for details.
What’s a GSS identifier?
Government Statistical Service (GSS) codes are nine-character codes which correspond to geographies for which national statistics are published, such as Middle Layer Super Output Areas (MSOAs) and Lower Super Output Areas (LSOAs). You might also see them referred to as Census or Administrative boundary codes.
Is there a list of boundaries supported by Government Statistical Service (GSS) codes?
| Boundary | GSS Code Prefix |
| -------------------------------------------------------------------------------- | ------------------------------------------------------------------------------- |
| Census Output Area (OA) | England - E00, Northern Ireland - N00, Scotland - S00, Wales - W00 |
| Lower layer Super Output Area (LSOA) | England - E01, Wales - W01 |
| Middle layer Super Output Area (MSOA); Intermediate Zone (S) | England - E02, Wales - W02 |
| Civil Parish (E/S); Community (W) | England - E04, Wales - W04, Scotland - S35 |
| Ward or Electoral Division | England - E05, Northern Ireland - N08, Scotland - S13, Wales - W05 |
| Unitary Authority | England - E06, Scotland - S12, Wales - W06 |
| Non-Metropolitan District (two-tier) | England - E07 |
| Metropolitan Borough | England - E08 |
| London Borough | England - E09 |
| County | England - E10 |
| Metropolitan County | England - E11 |
| English Region | England - E12 |
| Westminster Parliamentary Constituency | England - E14, Northern Ireland - N06, Scotland - S14, Wales - W07 |
| European Electoral Region | England - E15, Northern Ireland - N07, Scotland - S15, Wales - W08 |
| Community Safety Partnerships | England - E22, Wales - W14 |
| Police Force Areas | England - E23, Northern Ireland - N23, Scotland - S23, Wales - W15 |
| National Parks | England - E26, Scotland - S21, Wales - W18 |
| Registration Districts | England - E28, Wales - W20 |
| Travel to Work Areas | England - E30, Northern Ireland - N12, Other - K01, Scotland - S22, Wales - W22 |
| Fire and Rescue Authorities | England - E31, Northern Ireland - N31, Scotland - S38, Wales - W25 |
| London Assembly | England - E32 |
| Welsh Assembly | Wales - W09, Wales - W10 |
| Scottish Parliament Constituency | Scotland - S16 |
| Workplace Zones | England - E33, Northern Ireland - N19, Scotland - S34, Wales - W35 |
| Census Merged Wards | England - E36, Wales - W39 |
| Local Enterprise Partnerships | England - E37 |
| Clinical Commissioning Groups | England - E38 |
| NHS England Regions | England - E40 |
| Census Merged Local Authority Districts | England - E41, Wales - W40 |
| Non-Civil Parished Areas | England - E43 |
| Public Health England Centres | England - E45 |
| Public Health England Regions | England - E46 |
| Combined Authorities | England - E47 |
| Integrated care boards (formerly Sustainability and Transformation Partnerships) | England - E54 |
| Strategic Clinical Networks | England - E55 |
| Cancer Alliances | England - E56 |
| County Electoral Divisions | England - E58 |
| Local Planning Authorities | England - E60, Northern Ireland - N13, Scotland - S44, Wales - W43 |
| Local Resilience Forums | England - E48 |
| Greater London Authority | England - E61 |
| 2022 Built Up Areas | England - E63, Other - K08, Scotland - S45, Wales - W45 |
| Scottish Parliament Electoral Region | Scotland - S17 |
| Local Health Boards | Wales - W11 |
Why aren't all of my ONS polygons displaying on the map?
The visual only supports the latest Government Statistical Service (GSS) codes from the Office for National Statistics (ONS). This means that historical codes are not supported, and the polygons for those geographies therefore won’t display on the map. Please [check on the ONS website](https://geoportal.statistics.gov.uk/) if the codes being used are historical ones.
Is Northern Ireland base mapping provided?
No, Northern Ireland base mapping is not supported by the visual.
Will GSS codes for Northern Ireland render on the map?
Some Government Statistical Service (GSS) codes for Northern Ireland are supported and the visual will display the appropriate polygon (for example, Police Force Areas). Please check which boundaries are supported by the visual by viewing the table in the *Is there a list of boundaries supported by Government Statistical Service (GSS) codes?* FAQ above.
Does the visual work offline?
No. As the visual relies on external OS and Office for National Statistics (ONS) APIs, it won’t work offline. If using the visual where an internet connection is unreliable, it may not perform adequately.
I can’t get access to the OS Data Hub to get an API Key. What should I do?
If your organisation already has an [OS Data Hub](https://osdatahub.os.uk/) account, then your organisation’s OS Data Hub Administrator needs to approve your access. Your OS Data Hub Administrator is probably within your GIS / Geospatial Team. If you want to know the contact details of your OS Data Hub Administrator, please reach out to your OS Account Manager or the [OS Customer Service Centre](https://www.ordnancesurvey.co.uk/contact-us/business-government).
Do you store any of my data?
OS doesn’t store any of your organisational data that you use within the visual or send to our external services. We log information such as the API Key you use, the time you make a request to an external service, the volume of points you require to be geocoded, and the number if OS map tiles you use. This is done to ensure that we can identify anyone abusing these services so that other customers don’t experience any disruption, and to help us understand how much traffic the visual brings to the OS Maps API.
Does the visual use any external services?
There are four external services involved:
* The first external service uses OS Maps API to render the basemap. The API Key is created via the OS Data Hub and used within the OS Power BI Map Visual.
* The second external service uses an API from the Office for National Statistics (ONS) to get boundary polygon data (for example, if you wanted to display Lower Super Output Areas (LSOAs) / Middle Layer Super Output Areas (MSOAs) polygons or any other ONS-supported boundary on the map). The only bit of data sent to the ONS ESRI services is the nine-digit code (GSS code) they use to categorise the polygons. This service is powered by ESRI’s ArcGIS Online and uses a US-based server for operations. When the visual first loads, it will reach out to the github repository URL to download a small file which contains the latest URLs for the ONS services, in case these have changed since the visual was compiled.
* The third external service is for geocoding postcode centroids or Unique Property Reference Numbers (UPRNs). Here, the only data sent is the postcode or UPRN in return for x / y coordinates to be displayed on the map. Even if a user tried to send non-postcode / UPRN data, the visual would detect this and NOT send the data externally – so it's only ever possible to send a postcode / UPRN. We don’t store any of the data you send us. This service is powered by ESRI’s ArcGIS Online and uses an EU-based server for operations.
* The fourth external service is for tracking use of the released (compiled) version of the visual. Anonymous statistics (identifiable only by the OS Maps API key being used) are sent to a Microsoft Application Insights tracking service containing information on things such as which OS Maps layers are being used, numbers of data points being added to the visual, size of datasets uploaded to the visual, etc. No visual data (from your Power BI data model or any uploaded datasets) are ever sent to this tracking service.
Because the visual is open source, you are free to browse the source code of the visual and satisfy yourself as to whether or not the visual's use of external services meets your organisation's security requirements; if changes are required to suit your organisation's requirements, then you are welcome to download the source code and modify it to make your own Power BI visual that suits – for example, by using different base mapping layers or removing the tracking (or pointing it to your own tracking service).
What does the visual being open source mean?
Following an earlier private beta trial, the OS Power BI Map Visual was released as an unsupported open source product in May 2026. This means that the visual is freely available for users to use as they wish. This freedom extends to using the code of the visual as a basis for making new custom visuals with potentially different behaviours. The [source code of the visual](https://github.com/OrdnanceSurvey/os-powerbi-map/releases) is available from the same GitHub location as the visual's installation file.
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.os.uk/more-than-maps/advanced-applications/os-ngd-data-in-dashboards/os-power-bi-map-visual/os-power-bi-map-visual-faqs.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.