A dense network of sensors within an increasing number of cities means we can interpolate the results from those sensors. With the help of algorithms and artificial intelligence techniques, we can estimate the air quality between sensors with very high accuracy. This we call ‘interpolated measurement’ and it results in a colored ‘heatmap’. The color intensity of the heatmap (that is, the area around each sensor) indicates the certainty with which we estimate the measurements in a given place.

The points on our map represent the location of the sensors, and their color mirrors the quality of air: from the best (green), above the permissible standard (orange) to health-threatening standards repeatedly exceeded (red).