- A presentation of citizens' sensors processing

What can we do with the community sensors regarding air quality awareness? A lot …

A few months ago, I tried to know if the community was processing a set of sensors and publishing the results locally. I did not find real initiatives but some ambitions. is a web site attempting to perform such a challenge in showing the processed results of a set of sensors over the Toulouse region (France) where more than 30 citizen sensors are operating as well as 12 official sensors. By calibrating the citizen sensors and correlating them with official sensors, we can draw a coherent map of the air quality over the region.

In addition the site presents some considerations regarding the humidity and temperature effects on the citizen sensors and how they can be corrected.

Sharing the perception of air quality between citizen with their sensors is an approach to make people more concoius and careful with their local environment. Hope this initiative can help you to develop a similar behavior and to embark your local community.


I strongly appreciate, being in Toulouse, that my little sensor is put to use :slight_smile:
Along with m two sons there it seems we count for 10% of the Toulouse sensors!
I’d love more insight on the debiasing process announced, not only by comparing with the City’s oficial sensors but also regarding the altitude of measurements, which we do fill when publishing our data.
Because indeed my own experience is by living 4th floor, particle levels are divided by 3 --and I never saw maps with altitude adjustments.
I also verified this altitude effect in Paris where I have a small flat (levels are quite higher, although lowering yearly)…
Maybe this phenomena is less true with pollutants other than particles, like ozone or the like -but on that I don’t have a sensor…
(I also appreciate, on Deciphair, the sentence where they proudly compare their local town with the larger city : Castanet Tolosan being some 4 Km away from Toulouse, the text basically explains that while the latter is, well, already dead, its growing evolution is now of importance for ALL citizens :smiley: )

Hello Hervé
Thank you for the two smiles you attached to your comments. :smiley
I am pleased to see that Toulouse people having active sensors are following the forum.
My objective too is to create a local community with the owners of sensor over Toulouse.
I did not assess the effect of altitude on the sensor measurements, but I fear it might be a bit tricky for various reasons:

  1. It is difficult to know the altitude of the sensors despite it might be mentioned in the data attached to the sensor ID. (however we can try for a couple of sensors)
  2. The particles flow is the combination of different phenomena:
    - the common flow over a global area (transported by the winds: ex mineral particules from agricultural/industrial activities or from Sahara for instance)
    • the local emission, for instance automobile traffic in a street.

If your are living in a busy street/avenue whose traffic emission is the major factor, it is not surprising to see a différence in measurements between ground floor and 4th floor of a building; indeed imagine that the emission in the street is through a cylinder, the corresponding flow you are measuring is proportional to the surface of reception so to the distance of your sensor wrt the source. A sensor at ground level (5 m from the source) receives 3 times more particles than a sensor at 4th floor ( between 13 to 16 m from the source). The same phenomenon / effect is measured between a sensor on the ring road and a sensor 50-100 meters away.

I have noticed that some sensors are located at the same geographical point; either some owner may have several sensors or these sensors might be in a building at different floors; in the assessment I consider only one sensor in a very small area. If you want to know more about your sensors send me a message through the contact form in the web site with the sensor IDs.

If you are interested by exchanges between citizens in Toulouse on this topic, we can meet in Toulouse (bistrot!) or you can participate to meetings/conference we are organizing at “Le grenier - Castanet” or
to register in a group through the ACTR running workshop (ACT’R Toulouse – Réseau des acteurs de l’air)

Hope to meet you