Air quality modelling and estimation methods

Estimating air quality in a geographical region uses a remote server module 208 to receive air quality data from sensors and generate an air quality model. The module 208 receives first air quality data from a fixed field based sensor 202, the first data being measured during a first time period, and receives second air quality data sensed by at least one mobile vehicle 204 at at least one location relative to the fixed sensor, the second data also being measured during the first time period. The module generates an air quality model for the region using the first and second air quality data. To provide an air quality estimation, the server module receives third air quality data from the field sensor at a later time and uses the model and third data to predict air quality in the region. Climate data may also be used in the trained model.