Fig. 3.

Tree structure of the decision tree model for the prediction of NO2 built from principal components computed from hyperspectral down-welling radiance measurements. Nodes show principal components and their threshold value for the model. The leaves show the distinguishable NO2 values and their proportional percentage of occurrence, which can be still differentiated on the assumption that R² increases by at least 0.01 with each step of increasing tree-complexity.