Fig. 8

Result diagrams of key bands for all groups of soil data. Bottom figures are the wavelength selection results of all particle decomposed soil data by using uninformative variables elimination and successive projection algorithm. The rest of the pictures correspond to the selection results of different particle size data. The left figure shows the b-coefficients associated with the partial least regression cross-validation models (k=10) for predicting the STN. The horizontal lines represent thresholds for the b-coefficients based on the standard deviations of the STN. The diagram on the right is the bands selection result of SPA, where red scatters represent the selected key bands