The data for these figures are provided in sets of columns, with the hourly data for Kardinaal de Jonge, Breukelen, Griftpark and Cabauw. The first column has the raw sensor data and the second the official data. Sensor data consist of the average of the co-located sensor (not on Griftpark) and all sensors that pass nearby in an hour. The last column is for figure 6 and provides the calibrated sensor data for Kardinaal de Jonge using the Leave Station Out method described in the text. All concentrations in microgram per cubic meter.