Sources & licenses
All NO₂ values on this site are tropospheric column densities derived from satellite measurements. They are medians over city boundaries and calendar months, computed for this project, and are not ground-level concentrations.
Data
| Data | Source | License |
|---|---|---|
| Tropospheric NO₂ column |
Contains modified Copernicus Sentinel data (2018–2026),
processed by ESA. Sentinel-5P TROPOMI Level-3 offline product
(COPERNICUS/S5P/OFFL/L3_NO2), accessed through Google Earth Engine.
|
Copernicus Sentinel data: free, full and open access (Delegated Regulation (EU) No 1159/2013). |
| City boundaries | European Commission, Joint Research Centre (JRC): GHS Urban Centre Database (GHS-UCDB) R2024A, from the Global Human Settlement Layer. A 20 km buffer is used where no urban-centre polygon matches. | CC BY 4.0 |
| City list, coordinates, population, population density, capitals | United Nations, Department of Economic and Social Affairs, Population Division (2025). World Urbanization Prospects: The 2025 Revision, Online Edition. Copyright © 2025 by United Nations. | CC BY 3.0 IGO. Data were processed (selection, aggregation); the United Nations does not endorse this site. |
| Income groups | The World Bank: Country and Lending Groups / Country Analytical History. | CC BY 4.0 |
| Base map | © OpenStreetMap contributors, served from this site as a vector-tile extract built with Protomaps. | ODbL 1.0 |
| World map outlines (analysis charts) | Natural Earth | Public domain |
Software
| Component | License |
|---|---|
| Leaflet | BSD-2-Clause |
| protomaps-leaflet | BSD-3-Clause |
| Plotly.js | MIT |
| Inter (typeface) | SIL Open Font License 1.1 |
| Lucide (icons) | ISC |
| Django, GeoDjango | BSD-3-Clause |
| Dashboard source code | MIT |
Full license texts for the bundled front-end libraries are shipped with the site files
under /static/vendor/LICENSES/.
See also the legal notice (Impressum) and the privacy policy.