Caeli launches pilot with the Province of Zeeland to map ammonia emissions
Municipalities that want a clear picture of local air quality often encounter the limitations of the national monitoring network. In Helmond, for example, the nearest representative monitoring stations for pollutants such as NO₂ and particulate matter are located in Eindhoven or Vredepeel. These stations are ultimately too far away to provide a reliable picture of air quality in Helmond itself.
Since 2023, the municipality has been addressing this gap with an additional data source: monthly satellite measurements of air quality, combined with ground-based measurements and a specially developed AI model.
Data sources and applications
The satellite measurements were not obtained through a procurement process, but through a donation. Former mayor Fons Jacobs won the data at a conference and subsequently transferred them to the municipality.
With funding from the Clean Air Agreement (Schone Lucht Akkoord), the initiative received structural support in 2023. Since then, Helmond has been using the satellite imagery to identify areas across the city where particulate matter and nitrogen dioxide concentrations are higher or lower, and how these pollutants are distributed.
Added value compared to existing monitoring methods
The main difference compared to the RIVM's GCN concentration maps lies in how frequently the data are updated and their local level of detail.
The GCN maps provide annual average concentrations, whereas satellite data are updated monthly. This makes seasonal peaks in pollution levels visible, even when annual average concentrations remain within regulatory limits.
Satellite imagery does not replace existing monitoring methods but complements them. Helmond validates its own data against the National Air Quality Monitoring Network and combines them with local initiatives such as the Helmond Monitoring Network and the Innovative Monitoring Network of the Southeast Brabant Region.
Next steps
In the coming years, Helmond will investigate whether satellite data can be combined with other data sources to distinguish between general background pollution and emissions originating specifically within the city.
Traffic has already been identified as an important contributing factor. The municipality also wants to investigate whether neighbourhoods with greater health inequalities are structurally exposed to poorer air quality. This will help target future measures more effectively.
The role of satellite data at Caeli
At Caeli, we recognise a broader development in Helmond's approach: municipalities need access to reliable, local data that complement the limited coverage of national monitoring networks.
Our Air Quality Monitor is designed to address precisely this need. Satellite observations are combined with advanced algorithms to produce high-resolution air quality data that can be directly assessed against WHO and EU guidelines.
This enables municipalities, just like Helmond, to make informed decisions about where measures are needed most.
Scientific validation with high reliability
Because policy decisions of this kind require reliable figures, we have subjected our underlying model, Argus-AQM, to extensive external validation.
The model's nitrogen dioxide (NO₂) estimates were compared against more than 240,000 measurements from 3,616 official monitoring stations across Europe, covering the period from 2019 to early 2026.
To prevent the model from effectively 'favouring itself', entire regions were excluded from the training data during validation. This meant the model had to predict air quality in locations it had never encountered before.
The complete validation report is available upon request, and we would be happy to discuss the results in more detail.
For the Netherlands, the validation achieved an R² of 0.85 and the lowest error margin of all European countries included in the study, at 3.07 µg/m³.
These results demonstrate that satellite-based estimates, when properly validated, can provide a reliable complement to physical monitoring stations. This is precisely the role the data now fulfil in Helmond.
Would you like to discover how satellite-based monitoring can provide valuable insights for your municipality? Feel free to contact Martin Smit at martin@caeli.nl or +31 6 55772285.