Initial data publication:
In order to display information in near-real time, data shown on the project website prior to completion of the project are provisional and subject to change as the data undergoes additional quality assurance checks. The initial data release in July 2019 includes NO₂ data verified through gold pod co-location or initial reference site co-location. For sites where neither of these scaling factors are available, data shown has been adjusted using the network-based calibration method if the associated R2 parameter is sufficiently high. As additional gold pod co-locations are completed, scaling factors from those co-locations will be used in lieu of the factors determined through the network-based method.
To see which method has been used at an individual site, download the site information file.
The full dataset, including all pods, can be downloaded here. The data file and accompanying site information file will be updated monthly. Because data is subject to change with additional QA/QC, it is recommended that users download a new data file each time they wish to work with the data, rather than using a previously downloaded file.
Breathe London data is licensed under the Open Government Licence.
Uncertainty of initial data:
For data scaled using the ‘gold pod co-location’ methods, initial estimates of NO₂ uncertainty at the EU limit value range between ± 10-20% for most pods. A minority of pods have estimated uncertainties of up to ± 40%. Uncertainty is generally lower at higher pollutant concentrations. The project team will be reviewing and updating these uncertainty estimates over the course of the project. The range of uncertainties may be attenuated as the project undergoes additional QA/QC.
Uncertainty in the network-based method data is estimated to be ± 25% at this stage of the project. Improved uncertainty estimates will be available as the project progresses.
For comparison, final ratified data from reference instruments in the London Air Quality Network have an estimated uncertainty for NO₂ measurements of ± 10% at the EU limit value.
The Breathe London data platform provides the data and visualisations for the Breathe London website. The platform is based on the Google Cloud, which enables user-friendly performance when querying these large datasets to provide graphs and visualisations, and ensures the replicability and scalability of the platform to other cities around the world. The platform is open-source and is capable of ingesting data automatically from AQMesh pods and also other monitor networks such as the London Air Quality Network and Defra’s Automatic Urban and Rural Network. The platform stores Stage 0 data and calibration factors separately, and supports the QA/QC process by allowing the technical team to modify calibrations and redact suspect data. Third-party platforms and apps can connect to the platform through standardized APIs. The Breathe London platform is developed and maintained by Cambridge Environmental Research Consultants.