Air Monitoring 23 Network as a Sensor pilot in Glasgow


Scotland has some of the most stringent AQ standards to be found anywhere in the world and has recently introduced a wide range of measures under Clean Air for Scotland 2 (CAFS2) aimed at further improving AQ across the country.


Glasgow is the fi rst Scottish city to implement a Low Emission Zone (LEZ) restricting vehicles older than Euro 4 as from June 1st 2023 and imposing fi nes for non-compliant vehicles. This project coincides with the introduction of the LEZ and has the potential to contribute to the understanding of how the LEZ can improve AQ in the city centre over this period. All other major Scottish cities are also implementing LEZ’s during 2024.


The AQ pilot in Glasgow, Scotland, is organised into two key phases:


Phase 1 (June 2022 – Present): This fi rst phase is designed to test a range of different AQ sensor systems from a number of manufacturers attached to a major cellular transmitter in a central location in the city of Glasgow. At this location, the large array of AQ sensors is exposed to well mixed air volumes allowing direct comparisons of sensor performance during Phase 1, as shown in Figure 2. The sensors are measuring NO, NO2


, O3 , CO2 , PM10 , PM2.5 at 1-minute intervals. Reference AQ


data is available from a nearby conventional monitoring station operated by the city and this is enhanced by an additional reference-grade CO2


Cambridge University. Data is collected via the manufacturer’s online user interfaces and API services by Wireless DNA and made available for analysis by our partners from Cambridge University. A schematic of the end-to-end architecture is illustrated in Figure 3.


Outcome of Phase 1


Initial results show that proximity to a transmission tower has no discernible effect on the data quality (Figure 4). The out- of-box measurements form the sensor systems broadly track the nearby reference observations from Glasgow Townhead station (Pearson’s coeffi cient r>0.8 except for the CO2 of the PM2.5


instrument made available to the project by


Figure 3: Phase 1 end-to-end system diagram: AQ sensors are colocated on the same site in central Glasgow


and one of Platform 2) and the unique diurnal patterns in the


cellular transmission data are not observed in any of the sensor readings. Some candidates performed better than others and as a result those were chosen to feature in Phase 2 of the project.


Figure 4: Hourly average observations and network transmission data from 1 November to 7 December 2022 for co-located pairs of sensors nodes from three manufactures showing CO2


and AQ species including PM2.5 while the CO2 , NO and NO2 . Reference AQ data is from Glasgow Townhead urban background station is from a reference grade Licor instrument deployed for this study. Sensor data are out-of-box readings as provided by each manufacturer.


Figure 5 Phase 2 end-to-end system diagram: AQ sensors are installed on a number of sites in the city centre of Glasgow


Figure 2: Phase 1 test site: rooftop base station in central Glasgow, with a large array of AQ sensor attached to it


Phase 2 (June 2023 – Dec 2023): The second phase of the project has the objective of deploying a small network of devices across Glasgow and across a chosen city in Spain, whilst still operating the Phase 1 site as an additional node within the network and as a facility allowing the sensor manufacturers to provide updated test equipment for emerging sensing technologies. Figure 5 illustrates the end-to-end system diagram, whereas Figure 6 illustrates the type of high spatial resolution AQ data that Phase 2 will deliver.


The key objectives of Phase 2 are as follows:


- Demonstrate that the location of the cellular sites is compatible with AQ objectives in the test city and show the ease of installation on a variety of cellular site types


- Comparison of sensor data with that from existing reference grade monitors operated by the cities to demonstrate accuracy and reliability. As part of this, two different sensor types will be co-located at two reference sites in each city.


- Demonstration of the comparability of a network of at least 10 identical sensor systems over a period of at least six months demonstrating stability and proving our QA/QC measures


- Assimilation of monitoring data within a sophisticated AQ model (ADMS-Urban) in conjunction with CERC to further enhance the spatial coverage of the monitoring network by using the model to interpolate between test locations (10 metre grid squares) and use the emissions indices generated by the monitoring data to improve local emissions inventories used by the model. The model also provides the ability to predict local AQ up to three days in advance and can provide likely outcomes of “what if” scenarios providing essential input to control and mitigation strategies.


- Develop the sensor platforms in conjunction with manufacturers to optimise the performance of the sensor systems, reduce cost and scale the production of an “ideal” version of these technologies to be used at a commercial scale.


- Improve the data collection processes in conjunction with sensor manufacturers such that they can be successfully scaled for commercialisation. Automate device geo-mapping QA/QC, and validation processes which are being manually applied during Phase 1, to further reduce operational costs and provide near real time validation of data to be disseminated to clients.


- Advance the development of reporting and visualisation tools Figure 6: Map of Glasgow modelled annual average NO2 concentration for


2014, produced using ADMS-Urban for a previous project called QCumber- EnvHealth [7], which brought together CERC and the Universities of Edinburgh, Glasgow and Strathclyde with Transport Scotland. This map demonstrates the type of high spatial resolution AQ data that Phase 2 will deliver. Contains OS OpenData imagery © Crown copyright 2015.


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